Rates-Based Salary Basis error

Summary:

Hi experts,

I am trying to set up a new Rates-Based Salary Basis and faced with the following error:

The
value of the attribute VF Claimables: The value by criteria VF
Claimables must return a flat amount. Correct the value by criteria
definition. The VF Claimables rate definition couldn't be processed.
Review the associated error messages to diagnose the problem. isn't
valid.

I have no idea what the problem might be.

Can you please point me in the right direction?

Kind regards,

Volodymyr

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