Buggy Auto-Fusing With Cores

[spomp]

Not sure where the bug is, but it goes like this:

 

I want to fuse rank 9 Redirection to rank 10. Got 545 cores (133R, 94U, 318C). Clicking 'Auto-Fuse with cores' in upper part displays I have just 1 core left.

 

Looking what cores does the game suggest to fuse: it's 61 rare & 1 uncommon & 18 commons. If that is new algorithm, I am pretty sure it's not optimal - why would I use more rares than uncommons?

 

If algorithm is inteded to work this way, that display (1 core left) is surely wrong.

[5tarlight]

The rares give more experience so it likely uses as many rares as it can without overflow and then funnels in the low-ranks at an interval to prevent wasting experience.

The display is probably just wrong.