Row number in report column is treated as text

I’m trying to use an external CSV as input to a table view report.

I want to sort by [Row Number] which is indicated as a Number field. This is generated by Fibery I guess because the information is not in the CSV file.

But using the field Row Number in a column in the table view, it is treated as text and thus the order is not correct.

I also tried looking for a function to convert text to number but only find the other way around.