Item modal selection options – multiple selection + quantity

As you can see above I have the situation of an item modal where there are different variations, from which I can select different quantities or none. Currently there is a checkbox selection, and a quantity selection. If I select the checkbox, I have to add the quantity as well with a dropdown (quantities values are 10+ on average). If I select a quantity, the checkbox is automatically applied.

What is the best way to set up the UI? Should the checkbox option be removed completely, and have users just select the quantity? Should the quantity option be removed initially, and have it appear only when checkbox is selected?

Opinions/advice would be appreciated here. Thanks!