I agree with IT that it's tortuous syntax - but that would make the syntax mirror the message - plus you've beckoned the detective in me, so a stab at it - Call it solving a riddle what should be hours spent working ...

I think the "???" you are struggling with would best be filled by something like "peeler of apples to feed his granddaughter" ... The "what" in that line is indeed awkward and opaque - and partly because "what" is used in the prior euphemistic metaphor ("Call what branching ...") in the first half of the 'equation' and now in your line-in-question, the "what" introduces the second half of the equation ...

My first sense of the context for this poem's "story" was something like Chernobyl - or somewhere that a genetically transmittable trauma resulted from something violent or tragic that was transmitted to the granddaughter to make her fingers also move oddly ... But then it came to seem that, no the woman's odd finger movement was more in curious wonder and empathy with a grandfather who had been somewhere like the Holocaust and had been obliged in a concentration camp to torture - break others' fingers into angled branches (and sooner or later the same had happened to him) ... and how euphemism (and the grandfather's stoic and secretive survival strategy to make jokes out of the legacy of pain) served a kind of desperate forgetfulness and made him - and now the granddaughter too (by honoring the pain of his memories with silence) internalize and transform the twisting, distorting sensation of being 'broken' ...