I've got several input fields and such jquery code:
var amount1=$('.product-addon-wesprzyj-autora input').val();
var amount3=$('.quantity .qty').val();
var Total=(amount1*amount2*fractal*amount3)+(' PLN');
$('.product-addon-kwota-dla-autora input').attr('value', Total);
With the code you provided, I am not quite sure what your problem is. It could be a problem in your server side code where you save the data to the table. You need to debug and that find out.
But make sure that you are setting the form values properly so that your server side code will have the correct data from the form. You may consider using the
val() method to set value.
Also , when you read values from form inputs and use it for numeric operations, Consider converting the type to a numeric version by using
var Total=parseFloat(amount1)*parseFloat(amount2)*parseFloat(fractal) *parseFloat(amount3)+(' PLN');
Also, You may inspect your browser's network tab to see what data your browser is posting to the server code. That should help you to understand where your problem is.