"The first date in the top right-hand corner is the Office of Management and Budget (OMB) form expiration date. All government forms include OMB dates. The OMB validity date changes periodically and an expired OMB date does not invalidate the I-94 record or form."
That's just the expiration for the OMB approval, it explains what this is for at the bottom in small text.
https://open.defense.gov/Regulatory-Program/Process/OMBApproval/
https://www.cbp.gov/sites/default/files/documents/502386%20-%20I-94%20Fact%20Sheet_OFO.pdf
"The first date in the top right-hand corner is the Office of Management and Budget (OMB) form expiration date. All government forms include OMB dates. The OMB validity date changes periodically and an expired OMB date does not invalidate the I-94 record or form."