Hi sk01,
I have knowledge of misspelt first/last names by the USCIS even on approvals. So, they should overlook this typo-error, which is again not on the main document, I-140.
In the meantime as musiclover suggests, it is always best to have a corrected copy handy and make it available to the USCIS, in case related RFE is issued.
Good luck.
DIGS