Multiple arp effects on same line documented?

What is going on when you use the Axx (arpeggio) effect in more than one effect columns? Is this documented somewhere, or is it considered to be something experimental to do on your own risk?

If you for example put a C-5 note with A3A and AC7 on the same line, I can clearly hear that an F (5th note from C) is included in the arp. The only reason for 5 to be in there would be if the algorithm did A+7 (-C). Could anyone describe the algorithm used? I could reverse-engineer it, but it’s a bit tricky.

Unless it recently changed, it’s supposed to just add more notes to the arp.

edit:

It definitely doesn’t work that way now. I don’t know what it’s doing.

I would assume the arp commands are simply added like most other commands, in this case A3A + AC7 becomes A3(+1oct)5(+1oct)