Energy consumption of powersupply beams

[Malacodor]

The blockBehaviorConfig.xml says the energy consumption of a powersupply beam block is 300 e per tick and the supply is 240 e per tick. The tick rate is listed as 0.5 and burst length is 2.5 s. The energy consumption per burst should thus be 1500 e and the supply 1200 e. I tested this by transferring energy from a fully charged core to an empty one. The empty core received exactly 1200 e, but the core with the powersupply beam lost ~1965 e. Is there a reason for the additional 465 e/burst or is it a bug?