The PLS 8 has eight true-bypass loops and one buffered insert loop.
Loops 1 to 5 are mono. Loops 6 to 8 are stereo-capable, and each of those three runs in one of three modes:
Mono uses the loop as a single send and return.
Stereo carries a left and right pair through one loop.
Split treats the tip and ring as two independent mono loops, which is where the extra count comes from. Three stereo loops in Split give six logical loops, so five mono loops plus eight from the stereo section reach 13.
Chain order is not fixed by the panel. A crosspoint matrix sets it, and the order is stored per preset, so two presets can run the same pedals in a different sequence.
When reporting a routing problem, write the loop numbers and the mode each stereo loop is in.