I think I've found the bug. The individual convoy loss events for a time span don't get aggregated properly, introducing extra items. For example the six individual events
- GER sinks 5 ENG convoys
- GER sinks 7 FRA convoys
- GER sinks 4 FRA convoys
- GER sinks 8 ENG convoys
- GER sinks 3 ENG convoys
- GER sinks 9 ENG convoys
Should be aggregated into ENG: 25, FRA: 11
Instead it ends up as ENG: 25, FRA: 11, FRA: 4, ENG: 20, ENG: 12, ENG: 9
So if the top two items show different flags, those numbers are probably correct but the third line and the total will typically over-count by a lot.