Due to connectivity issues getting to Providencia used to be even harder than to getting to San Andres, nowadays you can get there pretty easily by using one of the 2 airlines that cover that route daily or the catamaran that sails every other day.
On any given day there's at least 4 flights going to Providencia and 4 flights coming back, that's 68 seats on each route, the company that runs the catamaran operation offers around 70 seats everyother day