Just that the pin outs are showing Q4-Q7 on pins 11,12,13,14
But that pinout is for the 20-pin version that is not a PROM. The data sheet is about the 18-pin PROM, except the pinout on page 2.
Actually, if look at the DS in the OP first post (but not in any other I could find online), you'll see that on page two a 20-pin pinout is shown.
That pinout, though, seems to be for a 512x8 bits memory (still 4096bits), such as maybe a DM54S472, so it has only 9 address lines but 8 data lines.
Probably an early, wrong, version of the datasheet.