Well then it is certainly achievable, because i have done it. If you look at the video from this post How to view your Live Data in Wappler Design View on a secure page, what you will see is that each of those products are inside a repeat, and each product has a form field with a custom quantity selector, that i can increase or decrease, and that i have customised further by not allowing keyboard input other than up and down arrows, and that all works as expected. Maybe it is slightly different though than your setup, would have to see your page live to determine.