What do I put in the box for withholdings?

Whatever is in the withholding box on your form.    What tax form are you entering?  

Form 2210 Line D

Line 6 of form 2210

This number is usually line 25d of your current tax return.

The IRS instructions for form 2210 are on page 3:

Enter the taxes withheld shown on the following lines: 

• Form 1040 or 1040-SR, line 25d; 
• Form 1040-NR, lines 25d, 25e, 25f, and 25g;
• Also, Schedule 3 (Form 1040), line 11, if you filed the above forms; 
• Form 1041, Schedule G, line 14. Filers of Form 8689,