Thanks for reaching out to us here in the Community, geolea.
When setting up an employee deduction, we can indicate the annual maximum limit that'll be taken out from their paycheck. However, we are unable to show a deduction limit for 40 hours.
Check out this article for the complete details: Retirement plan deductions/contributions.
I'd be more than happy to assist if you have more questions about QuickBooks Online. Have a good one.