How To Fix WXP015 - Errors occurred in the key figure formula type "after input"

SAP Error Message - Details

• Message type: E = Error

• Message class: WXP - Retail Planning

• Message number: 015

• Message text: Errors occurred in the key figure formula type "after input"

What causes this issue?

Key figures are used in this planning layout whose values were
calculated using key figure formulas.
Errors occurred in these calculations. Verify which key figure are
proving to be problematic.
To do this, use the "Checks for key figure formulas..." under "Extras".

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.