A lighting standard is to hang a chandelier about 30" from table to bottom of fixture. Most tables about 30" tall so the fixture is about 60" off of the floor. Adjust to suit yourself. If the dangling crystals are about 6" then this is about what they told you.

I do prefer hanging light over the dining table. There is something very cozy about it. But I see how semi flush or flush or sconces or even big overhanging floor lamp can be beautiful too, in some cases. I don't like flush mounts or so I thought; but when I suddenly saw one that I really loved-I changed my opinion in a blink of an eye, and didn't rest until I found place for it:) So it depends. What I don't like-a huge amount of recessed lights..they're okay in kitchens or hallways or where they are really needed, but I saw several rather pretty houses that had just these recessed lights all over the ceilings, a lot of them, everywhere. And the ceilings were perfectly high too, so I truly could see no reason for them..it just brings unwanted attention to these lights, and you can't look away somehow.

I would just put one crystal chandelier up. My table seats 10 and it uses that 110 inch length dining room tablecloth. That is plenty of light, and plenty of crystal drops to dust !! LOL... https://www.birchlane.com/furniture/pdp/hooker-furniture-treviso-extendable-dining-table-hkr11758.html or https://www.birchlane.com/furniture/pdp/west-point-extendable-dining-table-gryl2019.html or this one reads seats up to 12 when extended: https://www.overstock.com/Home-Garden/Simply-Solid-Corina-Solid-Wood-11-piece-Dining-Collection/10208353/product.html?refccid=2A2V23YRBESKP42N5BQQ74FKUA&searchidx=30 Keep in mind that today's "formal" dining sets don't have to be as intense a 'dust collector' as of old. It's all in the accessories, table cloths, dishes, and table decor to make it as elegant as you want it to be. And the more different looks it can give you, the more use you will get out of it !! https://www.overstock.com/Home-Garden/Simply-Solid-Corina-Solid-Wood-11-piece-Dining-Collection/10208353/product.html?refccid=2A2V23YRBESKP42N5BQQ74FKUA&searchidx=30 Now, I like the Hooker line and there are more, so keep looking. You might check with Nebraska Furniture Mart(the biggest store ever, in more than just one state now) and with Mathis Brothers out of Oklahoma City. Either one may have several dining options for you to look into. ..Overstock is good, but when you want something this big, you want to make sure the quality is similar /equitable to the size. I did not check out Wayfair or Grandin Road, and there are more places. I know a brand that makes what you want, I just have a hard time figuring out if it was Hooker? Possibly it was. Unbelievably, I have seen more beautiful gorgeous dining room furniture from the 80s in estate online adv. sales in metro areas this past winter than ever before. No one wants Mom or Grandma's 'family heirloom' dining room set apparently and they are usually very reasonably priced. Keep your eyes open, they are lightly used and they are a piece of art compared to many of what you see today. And alot of times, the silver, and the china, the hutch and the buffet are all there to go out the door with the furniture(Yes, even the Chandeliers too !! I have seen). Good luck. Don't settle, What you want is out there and keep your eyes open for those 'fire sales'...

How tall are is the ceiling in the room? If you search blogs some say for an 8' ceiling the height from the table is around 30-34" for an 8' ceiling, for higher ceilings they usually add 3" for every foot. IMO this is a matter of personal preference. I personally would never put a chandelier at that height because it's right on top you when you sitting down and its in your face when you standing and trying to talk or pass something across the table. The ceiling in my dining room 17' high, my light is 5'7 from the table and it's perfect. If you tell me your ceiling height and the table size I will give you a visual how it will look with a few different heights in relation to a person standing next to the table.