The amount shown on my 2210 line 6 does not match the amount shown in my W2 withholding. This appears to be a system error.

Line 6 of form 2210 include the taxes withheld shown on the following lines: 

Please check to see if any of these other withholdings effect your line 6 totals.

• Form 1040 or 1040-SR, line 25d;
  • Includes
    • W-2
    • 1099-S Proceeds From Real Estate Transactions
    • Ither forms
      • Form 1040-NR, lines 25d, 25e, 25f, and 25g;
      • Also, Schedule 3 (Form 1040), line 11, Excess social security and tier 1 RRTA tax withheld .
      • if you filed the above forms;
      • Form 1041, Schedule G, line 14. U.S. Income Tax Return for Estates and Trusts
• Line 25c— Form(s) W-2G.  shown in box 4.
• Form 8959, line 24, in the total on line 25c.
• Schedule K-1.
• Form 1042-S, Foreign Person's U.S. Source Income Subject to Withholding
• Form 8805, Foreign Partner's Information
• Form 8288-A. Withholding on Certain Dispositions by Foreign Persons

All of these can impact line 6 of the 2210.