Dependent's amount corresponds with step 3 from your employee's Form W-4:

The old W-4 used to ask the employee for a number of dependents. However, the new W-4 asks for a dollar amount. Here’s how to calculate it: If their total income is $200k or less ($400k if married) multiply the number of children under 17 by $2,000 and other dependents by $500. Add up the total.

If the employee's W-4 on file is in the old format (2019 or older), toggle "Use new Form W-4". Your employee is currently not required to update it. If they do need to update it for any reason, they must now use the new Form W-4.