Variable pay cannot be considered for ESI ded beco'z it is not determined as constant component of the earnings.
This variables may or may not be paid by employer at times , since that will effect your ESI contribution every month (EE & ER).
Consideration of Fixed earning components (which depends on present days) are to be considered for statutory deductions.
Hope above clarification would be helpful for you
21st July 2017 From India, Bengaluru
22nd July 2017 From India, New Delhi