Here is the demo, you can add more conditions to determine what is closest number while dragging using onDrag, onThrowUpdate callback.
Also, how do you create your demos? I think I pointed out to you previously as well that you were using really old version of everything. Your current demo was using 1.17.0 which I guess is older than 2 years. Always make sure you are using latest files, easiest way is to google 'GSAP cdn' which will show you links from cdnjs to all non-club files. To get links to club files visit this pen https://codepen.io/GreenSock/pen/OPqpRJ Which still points older files by version or two but still better than using year old files.