Thanks for your feedback
he only has to choose the quantity 50/100/150/… I just use the quantity option but the price is not correct in total, he multiplies the product price by 50.
example:
Product price: 0.18€ for 50g
Choice of quantity by step 50/100/150/200/…. which corresponds to the weight in grams.
If I choose 100g I should have this result 2×0.18€=0.36€