It's 1/2 granted fragment every 60 rolls, but you can't know when in that range you'll really get them.

Example:

You are at 840 rolls in kage treasure.

841-900 range will grant you 1/2 frags.

The same will be for 901-960 range.

But if you gained the frag for the 841-900 range at the 844th roll then you are granted to get your next frag before the 961st roll but for the 901-960 range it may even be the 959th roll.

So, in this case, the distance between the 2 frags would be 115 rolls, but you still gained the two granted drops for each 60 range.

Very likely this is what happened to you (you gained very early for the range you were in, even on a free roll, 1/2 frag in jin 1 treasure and now you have been unlucky on the following 60 range).

P. S. Basically you just were exceedingly lucky on your previous roll and quite unlucky on the current one, but if you put there another 22 ss you are granted to get it.