If he has 1.5mil gold in the storages he won't be looted 400k gold UNLESS his mines are somewhat full
If you are a TH8 and you get attacked by a TH10 the attacker suffers from 50% loot penalty, meaning he will only loot 150k gold and 150k elixir from your storages (remember the 300k lootable cap) + 1/4 of what's in your mines/pumps
So if you got looted 360k it means you had overall ~240k loot in your collectors (he could steal 60k of it)
All of this doesn't take into account the 1k/1k in yout TH and what could be in your clan castle (because you should always collect that anyway).
All these values are on the wiki in the storages' page



