Ability to sort the pivot table based on Iteration

Pivot table is created with Iterations as the Column headers. But unable to sort them based on the iteration numerically.

E.g. Sprint 1 to Sprint 10 is created. Sorting this in descending order alphabetically sorts the Sprints 9 to Sprint 2 correctly. But Sprint 10 comes in after Sprint 2, followed by Sprint 1.

Expected behaviour is Sprint 10 to Sprint 1 sorted in descending order.