An LED draws differently than an incandescent. This affects max load.
Dimmers also have maximum load requirements to ensure the load does not exceed the dimmer’s design limits. Surpassing these limits can result in premature dimmer failure, flickering due to noise, as well as breaker tripping. One of the main reasons dimmers have maximum loads is because of the inrush current caused by LED drivers. Inrush current is input current of short duration during initial start-up that exceeds the steady-state current value. The graph above shows the current waveform when a device is powered up.
Because of this inrush current, an LED may be rated as 25W but the actual wattage initially going through the dimmer is much higher. This means that if an incandescent dimmer is rated at 600W, you can’t assume you can use twenty-four 25W LED fixtures. A good rule of thumb is to allow 100W for each LED fixture so in this case, the 600W dimmer can handle only six LED fixtures.
The exact calculations vary for different reasons, but the best thing is just to take the manufacturer’s word for it with regard to any individual specification.