Why the exclamation mark? Do you think that's a lot or ridiculously little?

I really have no idea - my garden is larger than an allotment, on the other hand it's deliberately arranged to have as few as possible things that need regular attention and as much as possible where the attention required is not time-critical. But a full day in the garden each week and a few half-hour sessions doesn't seem wide of the mark, in either direction.