Available mana calculation calculates in some cases too much mana.

[LevelX2]

The changes committed with 81e5650972bf4e7f10df1dd3210c91838b72313d, fixed some problems with too less calculated available mana. But the changes don't handle, that e.g. a target can only be tapped once. So if you have two Birchlore Rangers on the battlefield, the calculated mana will be too much.

Related to cards like Seton, Krosan Protector, Urza, Lord High Artificer, Heritage Druid, Birchlore Ranger and Grand architect.

[JayDi85]

Same with sacrifice for mana (multiple instances of Ashnod's Altar). But that's ok to calculate too much (AI and players can play cards as normal).

[JayDi85]

Still actual (wrong playable calculation), use case from #8763:

[test too much mana]
battlefield:Human:Inspiring Statuary:1
hand:Human:Chaos Warp:1
token:Human:TreasureToken:1

Looks like playable code doesn't use mana activation limitation, real activate works fine: