GA Superman Census Question

[RedFury]

I was just looking through the census numbers of the early Superman issues and I noticed something strange. Maybe there's a simple explanation I'm not seeing, but both #11 and #15 have multiple entries. For issue 11, one entry says 7/8-40 (wrong date) and has 8 copies, while the other says 7/8-41 (correct date) and has 64 copies. Issue 15 has two entries as well, both with the exact same date (3/4-42), but one has 10 copies listed while the other has 18. Anyone have any ideas about what's going on here?

Thanks!

[aardvark88]

Very strange. Even if they were Canadian editions, the month of publication would only be about 1 month later maximum. Usually exact same month as USA issue date.