Dimmer capacity for halogen bulb
Halogen bulbs are technically incandescent bulbs. Therefore, the capacity would be 600 W according to the box.

According to topbulb.com,


  Halogen bulbs are technically incandescent light bulbs – illumination is produced in both when a tungsten filament is heated sufficiently to emit light or “incandescence.” The difference between the two is in the composition of the glass envelope and the gas inside the envelope.