When Thousand-Tailed Watcher gives enemy units -3M (minimum 1) and then Grand Strategem gives friendly units +5M, how do these modifiers combine? Specifically, with 1M tokens and 2M Faithful Manufacturers, what are the final Might values?

The correct final values are 6M for all units (both the 1M tokens and 2M Manufactors become 6M). According to a rule, when an arithmetic effect has a limitation (like 'minimum of 1'), it snapshots at the limited level when applied and is 'remembered' at that value for the duration. When Thousand-Tailed Watcher's -3M effect applies: the 1M tokens would go to -2M but the minimum of 1 limitation means they stay at 1M, so the effect snapshots as -0M (no actual reduction); the 2M Manufactors would go to -1M but the minimum of 1 limitation stops them at 1M, so the effect snapshots as -1M. These snapshotted values persist for the turn. When Grand Strategem later adds +5M: the 1M tokens become 1 + 0 + 5 = 6M, and the 2M Manufactors become 2 - 1 + 5 = 6M. The judges were incorrect because they didn't apply the snapshotting rule - they treated the modifiers as if they continuously recalculated together (-3M + 5M = +2M net), but the 'minimum of 1' limitation causes the Watcher's effect to snapshot at its limited value when first applied, not recalculate later.