Text trim ! Help

I made a html page where I read numbers sent from arduino, now I need to multiply this number, but I have this problem:
So I need to get rid of the text on the sides and just leave the numbers.
I found some blocks for getting only numbers from a label, but it messes up my number output (my number is 51, but reads it 15?!?!).
This is the topic from which I used the code:
[Remove characters and retain only numbers from string]

You need the Taifun parse procedure for this, giving it the two html tags as prefix and suffix.