Switching from table to graph give wrong data

Question

I'm using the Drupal Commerce Report module as a base for my stats. I have a table which give me data about my sales per month.

I'd like to use graph instead of table, to make it easier to compare. For some reason, the coma is gone, so all my sales reports are wrong

I tried to alter data in a pre_render, in a preprocess (by checking the format, test with a dot instead of a coma) but still having the wrong result