Your tax reports display the total proceeds and cost basis of all your swaps throughout the tax year.
The total refers to the total USD value of all your swaps and sales throughout the year. So if you have $10 in USDC, and swap it to USDT, that's $10 in proceeds. If you swap that same $10 back to USDC, that's $20 in proceeds, even though you still have the same $10.
That total adds up quickly and is usually larger than people expect.
The number that matters for taxes is the net, which is:
Total proceeds - total cost basis = total capital gain/loss.