The key difference between “at least 1” and setting a larger number of slots to a task, is that having “at least 1” with one signup means that the task is filled. For example, we need at least one person to sign up for cleaning, but we’d like to allow additional signups if more people can help. If we just have extra slots to sign up, it gives the appearance that the task is not actually filled.
So, you are basically wanting some option that lets you accept more signups for a task/item, even after it is “filled” (initial # of spots assigned have been filled). There is nothing built-in to do that, and this is not a small or simple bit of code to add either. Basically would need to create a new database field in the tasks table to determine if more signups can be allowed after it is filled, plus add the new fields to the admin form, and all the required functions for saving and retrieving that field data. Then somehow have to change how those “filled” spots are displayed to still allow more people to sign-up (and to let them know that they can sign up), and make that different than the filled slots that do not allow additional sign-ups, and somehow do all that without breaking current installations of the plugin.
You could add that in the feature requests section, but probably not something I would add on my own as there are simply far too many feature requests to keep up with for a plugin that doesn’t even come close to paying for the time spent on developing/maintaining it (since mostly volunteer organizations use it, and they never seem to have money to support development or buy add-ons).
I might consider that as a possible subsidized feature. So far, though, this is a very specific request, and not something that anyone else has asked for.