Every time you start a bot, it counts as a full hour.. so you started it at 10:36, that takes 0.12 credits.. you started again at 10:37, it counts as a full hour and takes 0.12 credits
Perhaps the ability to request refund automatically if a bot fails to run for more than a minute or two would be nice? I'm getting a lot of "Runemate has lost its bridge" errors on expensive bots and going around asking for refunds is tedious