Once again I was playing the same cheesy NR deck that exploits sword + vernon roche, which seems to have been at least 50% of my opponents the last couple of days. His last card was vissegerd. As you can see in the screenshot, he has 5 boosted units, 7 units overall. So he should have had 6 charges, 1 + 5 bonus. He got 8 charges instead, the targeted unit has been reduced from 9 to 1. And so I lost the match by a single point, instead of winning by a single point.
I know other cards can give extra charges, but that's not what was happening in the cases I noticed, Vissegerd hit the table with too many charges. I've paid more attention to it since first noticing it, and I suspect what is happening is that 'boosted unit' is also covering units that have had armour added, maybe also units that have had other statuses added. Both unboosted units in my screenshot do have armour, and I think it was similar in the game that prompted my first post, and I have had a couple of games where he had the correct amount of charges.