Farts actually stink only for the benefit of the deaf.....
ATA 28-10-00 General Description Fuel System
Supply tanks = 92 kgs
Main tank = 452 kgs
72 kgs of the Main tank capacity is actually in the upper undivided part of the Supply tanks above the "overflow channels". Granted this data is not in the cyclic attendants blurb.
92 + 72 = 164
522 - 164 = 358
92 = 56% of 164 which is where the fuel would be level with the bottom of the overflow channels.
Therefore 56% of 358 is 200 kgs. This would only be valid in the level position. 215 as quoted was a rough guess for Granny.
That's twice now MG or would you rather take HT's way and get the tools out and see for real?