How to wire ceiling speakers where each pair of speakers has only two wires total
You should put a meter on them and check the impedance. You could also pull a pair of speakers to see how they are wired.

Ceiling speakers are not an "audiophile stereo sound" setup, typically - they are designed to cover a large area so you can hear the sound all over the house (or area they cover.)

Two typical (hardly the only) ways you might get what you have are a pair of 4 ohm speakers wired in series to make 8 ohms, or a pair of 16 ohm speakers wired in parallel to make 8 ohms again, since many things like 8 ohms for speakers. At work I have a pair of 8's wired in series to make 16 on a system that is exposed to abuse, in an effort to help the speakers survive the abuse...

Other things you might see (particularly in ceiling speakers) would be a transformer and tap (reconnectable wire) on each speaker intended for a "70 volt" speaker distribution amplifier.