Please explain coins

The pokemon earns 1 coin every hour it defends a gym. As far as I know, it earns coins til it returns but you are limited to only receiving 100 coins per day. So if it returns with more than that, or multiple pokemon return with more than 100 total, you just forfeit the excess

There's no cap at 10, I just got 12 coins for holding a gym 10 hours.

i dont know. Gyms have only been open for 1 day now. What i do know is you get 1 coin per hour your mon is in the gym. But you can only get coins, once you pokemon is kicked out of the gym. ie. so 24 a day x 3 days is 72 just for that one. But lets say you lost 5 gyms, you dont get 72 x5 =360. The max you can get daily is 100 coins

I believe if they add more incentive like a pokemon of yours holds a gym for 24 hours, you get 20coins right there.

I've figured it out. It's 1 coin per hour defended per Pokemon. It's based on a 24 hour period as well. Already collected my 100 coins for the day.
Had 95 coins then had a Golem that's been defending for almost 13 hours come back with only 5 coins.

No way I've had a Charizard and Golem both over 14 hours of defending return with 0 coins. This means I have to wait 24 hours from which I first dropped for my counter to reset to start collecting coins again.

Got 102 coins since gyms were opened 22 hours ago. Didn't expect more than 100 would be possible.