This is what should happen on most grout holes. The take is neither very fast nor very slow.

The starting mix is suitable; a moderate, steady pressure can be held. The surface level in the agitator falls so slowly that it has to be stared at for about a minute to notice a drop (exaggerated in this presentation). The starting mix can probably be followed by thicker grout successfully.

There is a definite, though mild and possibly sluggish, response on the pressure gauge when settings of the control valve are changed. This is in contrast to the immediate response produced in relatively tight conditions and the lack of any response at all in a fast hole.