You do NOT calculate the income. Contact the trustee and tell them you are removing an excess contribution for 2024 of $4150. they will calculate the income. Some HSAs allow you to submit the paperwork online.
because the funds are invested it may be best to call rather than submit a form online.
*
the other option is to leave the money in and pay a 6% penalty (~$240) on the smaller of the HSA contribution or its Fair Value on 12/31/2024. The $4150 counts against the maximum contribution for 2025 ($4300 self-only) so you can only contribute an extra $150. You also have to be covered each month to make the max.
There is also a last-month rule that allows you to make the max even if not covered by a HDHP for each month of 2025. These rules require you 1) to have HDHP coverage on 12/1/2025 when you are not covered by a HDHP for each month of 2025 in order to make the maximum and 2) you must maintain HDHP coverage for certain months in 2026. Failure and the excess is taxable along with a 10% penalty. See IRS PUB 969
