modify javascript code

hello,

I'm a french teacher and I apprécitate most of h5p tools.

At the present time, I'm using Arithmetic Quiz but I'm not fully satisfied. In fact I miss the possibility of choosing which addition/substractio/multiplication/divide table : for instance I'd would like to choose only additions with 9 : 2 + 9 , 23 + 9, 42 + 9 etc.

I tried to modify the js file which randomize the numbers but it doesn't work. However I've succeed to change css files and sounds.

Anybody can help me ?

Thank you.