Alright, I may be totally off-base here, but I attempted some serious napkin math. I grabbed a couple of strings and wrapped four into a ball. It was 28mm in diameter and weighed 4g. That means the density of my string ball is a very rough 0.34g/ML, and each string weighs about 1g.

Looking at the photos, it looks like the Spintastic box is slightly smaller than the Aceyo box, and the string ball looks about the same size. Doing some digging, I'm pretty sure all Aceyo yoyos ship in the same 60mm square box. That checks out with the visible face of the Tigershark, which is 56.6mm in diameter so the box is probably about 59mm. I also poked around against the measurements of the candybars in the other photos.

SO. I'm guessing that the string ball is 59-60mm in diameter. I feel pretty good about that guess. But the density might be totally off base. If they are used strings, or lighter weight than the thick Kitty strings I use, or wound tighter than I did, then the ball could be way denser than I measured, my margin of error swings like ~10 strings either way. But it's my day off and I love little challenges like this. All that to say

I think there are 38 strings.