It’s still going to do the check to see if the # of existing signups for the task is more than the quantity entered in the form, when you submit the form. No way to turn that off.
The options at this point are to either clear some of the signups to get the number back down, or you can manually edit the task description in the database (like you did with the quantity). Or, temporarily edit the quantity again to be more than the # of signups, so you can then make any changes from the admin dashboard you want to make to the descriptions, then set it back in the database to the # you want.
Note, that if this is something you need to do quite often, then perhaps instead of using the Recurring type for the sheet, create a single event sheet, and get it all set up the way you need for the first date, and then use the “Copy” feature in the list of sheets to create a new copy. Then edit the copied sheet to change to the new date, and repeat as necessary. That way you can freely change the # needed for each task for a specific date without coming across this particular issue.
This was initially setup as a feature for our own PTA web site so that the signup sheet managers wouldn’t accidentally reduce the # of signups below the number of people who have already signed up for an event. It’s not a “bug”, so not really a support issue in that sense. I could certainly modify the code to get rid of that check, but then that opens up another set of issues on which signups get deleted for that task? That’s why there is the ability for the admin to clear any signups right now… if you need to reduce the # available for a task to that below the number that are already signed up, then the admin needs to first pick which signups to clear to reduce the # of signups to the quantity you want. Otherwise, how does my code know which ones it should clear? Granted, this is not ideal for the Recurring events since there is a shared task for each date, so you can’t adjust the quantity for just one of the dates… which takes us back to perhaps the best solution is to set this up as a Single event, and make copies as needed for each date. It’s not ideal, but it’s part of the database structure that I inherited from the original plugin that I start with (from another developer), that I modified for our own school’s PTA web site.