Some time ago, I posted on Literature about Sappho's Hector and Andromacha. To sum-up, the sources for that are P.Oxy. 1232 and P.Oxy. 2076. P.Oxy. 1232 is three scraps of papyrus, one of which has a big part of the poem in two columns, another one of which is considered to contain a different poem, and the last one is (for what I can tell) a tiny scrap containing the ending of some lines. The question at Literature was: the two-column scrap and P.Oxy. 2076 clearly go together, but the tiny scrap? Why is it together with those as well? Now once we have P.Oxy. 2076 we clearly see the lines in P.Oxy. 2076 join very nicely with those of the tiny scrap, which is reason enough to put them together. However, before P.Oxy. 2076, the only reason I can see to hypothize a link between the two-column scrap and the tiny scrap is the P.Oxy. number. So I was wondering:
Why are those scraps under the same number? And more generally, how are P.Oxy. numbers chosen for scraps of Oxyrhynchus papyri?