Tells me ent code L box 12 reimbursements from W2 but then says don't add reimbursements that were added to wages in Box 1 How do I know if were added to box 1 income

The IRS Instructions for the W-2 (these are instructions for your employer, not you) say

"Report in box 12 only the amount treated as substantiated (such as the nontaxable part). Include in boxes 1, 3 (up to the social security wage base), and 5 the part of the reimbursement that is more than the amount treated as substantiated."

If your employer completed the form correctly, then this means that the amount associated with code L in box 12 is the only the reimbursement that was NOT added to income on box 1. This also means that you don't know what was the amount of the reimbursement that was in fact added to Wages in box 1 (at least not from looking at the W-2).

It is possible that the employer made a separate entry in box 14 indicating the amount of the reimbursement that was unsubstantiated and therefore added to Wages in Box 1. But since most box 14 codes are up to the employer to decide (i.e., I can't tell you which code, if any, it is), you will just have to call the employer and ask what the amount was that was added to Wages in box 1.