Gonal f pen extra dosage

I made a mistake. Like an idiot I have been writing down the amount I take everyday. I have a 900 pen. Instead of reading the pen which said 37.5 (the 1st pen is now empty), I took another 37.5 on a new pen because then I would have the 75 I needed to finish my dosage amount prescribed. Then I went back to the instructions and it said it might not read the right amount bc they give you more medication in these pens. Damn it!