Hey,
Are you referring to a Step VS an accent ?
You can set a step to an accent step by hitting "Accent" then clicking on the step which is lit up to change it to an accent.
The contrary works, if a step is set to accent then simply hit "Step" and click on the red step to change it back to a standard step.
There are only 2 velocity levels on DrumBrute Impact : Step and Accent. The instruments are designed to work ( and only understand) with those two values. An accented step is typically louder but it also affects other synthesis parameters (a moderate amount of decay for example)
Hope this helps !
Victor