Issue with absence validation fast formula

Summary:

We got issue absence validation fastformula, there one field (L_DURATION2)is causing issue , no value coming.

We have updated the logic with the below logic.

if isnull(L_DURATION2) = 'N' then
(

L_DURATION2 = 0

)

Can you please anyone confirm on the above , whether we can this process of adding.

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