Thanks a lot, @tc_procare
It happens in all flows I create, like the one below. I make an Excel sheet with three columns (A, B, and C) and here two rows. I haven't got the "Read as text" and when inspecting the value, it comes out as a text as you suggest.

If I use the convert text to number before the expression, it works, but I would like to know how it can be solved within an expression (to save time over and over in the future).
This is my expression, which doesn't work: %CurrentItem['A'] + CurrentItem['B']%
I also tried to format the excel data as numbers, and no difference. I would love not to format Excel data, as that will make my PAD flows inefficient.