Unpaid leave Retro element is being exempt from social security subject withholding

Summary:

Whenever a retro element for unpaid leave, it results in exempt income for current month which is impacting social security withholding value

Content (please ensure you mask any confidential information):

Employee applied unpaid leave for the month of February on March and a retro element got created in March payroll which is correct.

Suppose monthly salary is 5000 , unpaid deduction is 1000, gross becomes 5000-1000(unpaid retro element) = 4000 this is also correct,

The expectation is social insurance employee tax should be calculated at 4000.

But its calculating at 3000 which is due to exempt income 1000

As 1000 was already reduced from gross , is it expected that 1000 gets reduced again in the form of exempt income.