Why does TurboTax calculate my capital loss used as more than $3000?

Your capital loss carryover is first used to offset any capital gain that you have this year. If that doesn't use up the carryover, up to $3,000 will be used to offset other income. So if you have capital gain, including capital gain distributions, it will almost always use more than $3,000 of the capital loss carryover. The total amount that's used is only limited to $3,000 if you have no capital gain.

Here's an example. Suppose you have a net capital gain of $2,000, other income of $50,000, and a capital loss carryover of $10,000. $2,000 of your loss carryover will be applied to the $2,000 of capital gain. Then $3,000 of the loss carryover will be applied against your $50,000 of other income. So the total amount of the capital loss carryover that's used is $5,000.