Making estimates are to only make sure you will not have an underpayment penalty ... so you can just pay the last one as is  but  you will probably have a balance due to pay on 4/15.  Or you can increase the last payment to reduce your eventual balance due.

What are estimated taxes?

https://ttlc.intuit.com/replies/3301588

Do I need to make estimated tax payments to the IRS?

https://ttlc.intuit.com/replies/3301891

Why did 1040-ES estimated tax vouchers print out? Do I need them?

https://ttlc.intuit.com/replies/3301872

How does TurboTax calculate my estimated tax payments?

https://ttlc.intuit.com/replies/3301730