Sometimes, the client specifies a certain number of gigs they want completed, but they post more gigs than that, because it's likely that less than 100% of the gigs will be able to be completed. When the number of gigs they want completed is claimed, then all the other gigs are Paused. Right now, the way you can tell a gig is Paused is that it will say it is claimed, yet it will not disappear from the map. The gig instructions may just show a blank page.
If some of the Gigwalkers who had claimed the gigs end up not completing them before their deadline, then the remaining gigs will become available on the map again.