If I understand your question well, you seek for a way to scale down the feed rate listed into the Gcode? To my knowledge, ground control does not offer this feature. But if it did, I think you would want to scale down the spindle speed along the feed rate to avoid starving and overheat the router bit.
Yet the maslow CNC firmware does not yet provide a spindle speed control… About this, you might want to look at this thread.
Greetings.