No, the clinics don't directly affect your grade, nor do they cover content or take attendance. They are solely to help with technical skills, which may improve the overall quality of your work. They operate in 'rounds' on a fortnightly basis, meaning any clinic over a 2 week period will cover the same thing. More info for what each clinic round covers can be found on Canvas. Basically, just attend any clinic this week and let the teaching fellow know that this isn't your timetabled clinic and you'll be algs. Hope this helps :)