The IRS knows:

https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-401k-and-profit-sha...

"Generally, you aggregate all elective deferrals you made to all plans in which you participate to determine if you have exceeded these limits. If a plan participant’s elective deferrals are more than the annual limit, find out how you can correct this plan mistake."

Is the person 50 or older?

"Highlights of changes for 2020

The contribution limit for employees who participate in 401(k), 403(b), most 457 plans, and the federal government's Thrift Savings Plan is increased from $19,000 to $19,500.

The catch-up contribution limit for employees aged 50 and over who participate in these plans is increased from $6,000 to $6,500."