What is 1C charge/discharge rate in battery instruction manual?
First,

'The "22Ah" implies a discharge rate of 1.1A over 20 hours.'


Only if the manufacturer says so. It might as well mean 22A over 1 hour, or any other combination that multiplies to 22Ah.

C is generally the capacity divided by 1 hour, so for your battery it would be 22A. Hence eg. 'charge at 1C' can be stated, independent from the capacity of a battery.