If we understand correctly you have some numbers in a data table column, that are plotted as titles on the category axis (Primary X) and you want to sort them as numbers. If this is the case you can follow these instructions:

1. Create a category grouping with the following grouping expression:

=Fields!YourTextField

2. Create a sorting rule for the category grouping with the following expression:

=TONUM(FIRST(Fields!YourTextField))

This should sort the category data groupings in ascending order and treat the strings as numbers.