Free in the first year, free in the second year after brushing six times. There is no limit to how much you can brush each time.
Almost all banks are like this, only saying that credit cards are valid for three years in the first two years, regardless of the third year.
I don't use China Merchants Bank's credit card, so I don't know the specific situation.
You can call their customer service and ask, their attitude is still very good.