Hello again @Dave_Baines,
the answer is different 
and I hope, I understood your question properly:
At the right side from an anchor dropped, you are able to improve as you want. There are several “tools” to do this: E.g.
- fixing the needle exactly where you want to drop an anchor and then drop anchor
- changing the speed of a track step by step
- changing the speed of a track by doubling or half speed (you need this, if you want to improve 6/4 rhythm to 4/4)
But don’t shift the hole grid by the arrows. You will move everything at the left side, what you just amended.
It’s a little bit difficult to handle this procedure and it takes some experience. I orient always at he needle and use my ears to detect, where to drop anchor or what to do else
Sorry, my English is not perfect as I’m not an English native speaker
good luck and enjoy the weekend
Brgds BeatMaster
taken from the manual, item “Beat Grid” page 35