Anupamain,
You have asked whether ESIC is applicable on gross earning of Rs.23K. Please note that at present the ceilings limit is Rs.15000/- PM and expected to be raised to Rs.21000/- per month (subject to final notification) and as such ESIC is not applicable on Rs.23000/- pm in the light of even proposed notification.
As far as ESIC calculations are concerned, you are liable to deduct 1.75% of earned wage / salary rounded off to next rupee and add employer's share at 4.75%.
P K Sharma