Please note that the 1099-B is representative of Notional Trading Volume.
Example: If a client funds their account via ACH for $5,000 (which automatically is traded into GUSD), and then convert the $5,000 GUSD into USDC, and then buy $5,000 worth BTC - this would all represent $15,000 on 1099-B. For this reason, you may see the amount reported on your 1099-B to be higher than account balance.