Cause
401K Match Formula 1 in the Help Topics is missing a parenthesis. This issue has been reported, and will be addressed in a future update.
Resolution
Correct formula should be:
MIN((LOOKUP(Amount[PR Check Deduct], Employee[PR Check], Period End Date[PR Check], Check Sequence[PR Check], "401K") * .5), Gross Pay[PR Check] * 0.06)