My advice, keep your own records (using the raw data eBay provides) on the revenue side and not worry about trying to reconcile your own numbers to what eBay shows on the 1099K unless they are WILDLY out of sync on the annual total.
If you choose to do that remember these are your taxes and your schedule C and your accounting method. If you rely on eBay's numbers you are using cash accounting for your own revenue records which you will have to declare on your schedule C. While this may simplify your revenue it may complicate your expenses since you will not recognize those expenses until they are actually paid. Anything you purchase on a CC would not be recognized as an expense until you actually paid the bill and the money was deducted from your account.
It also may create a conflict if you are receiving a 1099 from PayPal and/or Venmo for sales you make elsewhere since those two financial processors pretty much utilize accrual accounting and the money is available instantly. Accrual accounting also allows you to recognize an expense at the moment you make the purchase regardless of when the cash actually transfers. You can declare a personal hybrid form of accounting on your schedule C but that may prove to be a record keeping burden if you sell a lot of items across multiple platforms and venues and receive multiple 1099's.
I prefer to utilize accrual accounting and recognize the eBay revenue the moment the buyer pays for an item and expenses the moment I purchase an item regardless of when the cash is actually transferred. There are multiple accounting methods you can use to keep your own records and there is no right or wrong answer to which one you choose but once you declare on your schedule C it needs to remain constant from year to year.
