How does coin deduct subscription charge?

There is 50Rs. per month subscription charge. How and when is this deducted?
Monthly or quarterly or yearly
Fixed timeline or from the day you started subscription
Do I need to have the necessary balance in my account?

Coin subscription fees apply only when your total MF investments exceed 25k. On the day your total investment exceeds 25k, you will be charged Rs.50 and you will be charged Rs.50 on the same day the following month onwards, regardless of the amount of mutual fund units you buy.

Can I see the history of subscription deductions anywhere?

All your Coin subscription fee entries will be posted in your Q-backoffice ledger.

Suppose after certain period like 1 year. I have redeemed my investment and total invested amount dropped to 10000. So then also the subscription charges will be deducted?

Once you have crossed investments of 25k, Rs 50 is charged until you exit all direct MF and unsubscribe from Coin.

I don’t see it even though it is more than a month since I bought MF more than25k.
Coin subscription is enabled though.