What numbers should be excluded from Line 2, 5a and 5c on the 941 Quarterly payroll report

Here's a link to the instructions: https://www.irs.gov/pub/irs-pdf/i941.pdf

The instructions for the boxes you mention are:

Box 2. Wages, Tips, and Other Compensation
Enter amounts on line 2 that would also be included in
box 1 of your employees' Forms W-2. See Box 1—Wages,
tips, other compensation in the General Instructions for
Forms W-2 and W-3 for details. Include sick pay paid by
your agent. Also include sick pay paid by a third party that
isn't your agent (for example, an insurance company) if
you were given timely notice of the payments and the third
party transferred liability for the employer's taxes to you.
If you’re a third-party payer of sick pay and not an agent
of the employer, don't include sick pay that you paid to
policyholders' employees here if you gave the
policyholders timely notice of the payments. See section 6
of Pub. 15-A for more information about sick pay reporting
and the procedures for transferring the liability to the
employer.

Box 5a. Taxable social security wages. Enter the total
wages, sick pay, and taxable fringe benefits subject to
social security taxes you paid to your employees during
the quarter. For this purpose, sick pay includes payments
made by an insurance company to your employees for
which you received timely notice from the insurance
company. See section 6 of Pub. 15-A for more information
about sick pay reporting. See the instructions for line 8,
later, for an adjustment that you may need to make on
Form 941 for sick pay.
Enter the amount before payroll deductions. Don't
include tips on this line. For information on types of wages
subject to social security taxes, see section 5 of Pub. 15.

Box 5c. Taxable Medicare wages & tips. Enter all wages,
tips, sick pay, and taxable fringe benefits that are subject
to Medicare tax. Unlike social security wages, there is no
limit on the amount of wages subject to Medicare tax.