In particular, if you specify an objective tolerance with the relative or absolute solution pool gap parameters, populate stops if it cannot enumerate any more solutions within the specified objective tolerance.
However, there may exist additional solutions that are feasible, and if you have specified an objective tolerance, those feasible solutions may also satisfy this additional criterion. (For example, there may be a great many solutions to a given problem with the same integer values but different values for continuous variables.) Depending on the solution pool intensity parameter, populate may or may not enumerate all possible solutions. Consequently, populate may stop when it has enumerated only a subset of the solutions satisfying your criteria.