QB Issue Resolution:

Line 1 of your 941 form indicates the number of employees who were paid for the specific pay period that includes the 12th day of the 3rd month of the quarter.

Since you already submitted the form to the IRS, I recommend contacting them first before making any changes. They can provide recommendations if you still need to file the 941-X. For additional reference, you can also check these articles about the 941 form:

Resolution for Issue 'Just submitted my 941 quarterly form but left off the number of employees so what do I do? Help' available: Yes (Solved).
Source: Intuit Community forum.

Just submitted my 941 quarterly form but left off the number of employees so what do I do? Help: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for 941 quarterly
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for 941 quarterly [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: