First of all, thanks for coming and asking. This is something sellers discuss a lot as the misunderstanding does cause seller/buyer relationship problems.
I would suggest that in future you don’t go with a seller that offers unlimited revisions because this shows a naive or inexperienced seller and is risky for you.
Keeping it simple, a revision is a change, so as long as you’re not asking for something you didn’t originally ask for, then you can ask for a revision. For example, if you said you wanted a horse, but they gave you an alpaca, then you should ask for a revision. If you said you wanted a horse, they gave you a horse, but you want it brown, not white, you can ask for a revision.
If you said you wanted a horse but you changed your mind and now you want an alpaca, this isn’t a revision.
In terms of whether the design suits your preferred style, then if you gave them examples to guide them as to what you like, you can ask for a revision if their design doesn’t fit. If your brief was ambiguous, then you probably shouldn’t ask for more than one or two revisions because you don’t like the style. After 2 revisions you should be able to determine if the seller’s ever going to give you what you like. You may have to accept that some sellers will never understand and give you what you want.
A good idea of picking a seller for this type of work is to go to multiple sellers with the same brief at the same time, buying their cheapest offering, and see which one comes back closest to what you want. Then continue to work with that one.