Dimmable ballast question

I just got a 400w lumatek digital dimmable ballast. The setup came with a 400w HPS and a 400w MH bulb.
My ballast settings are 50%, 75%, or 100%.

What are these settings for?
Are certain settings better for each growth stage, veg and flower? Like.. should it be on 50% during the MH veg, then switched to 100% during the HPS flower?

Probably stupid questions, but I've gotta learn somehow..
Tried to find the answer online, but no luck.

Your questions are very reasonable.

Bottom line is: more light = more growth. People use the lower settings to 1) save energy costs, 2) reduce heat and 3) supercharge dying or weaker bulbs if you have the 110% setting. I guess you can reduce wattage to slow growth if necessary too.

I run at 100% always. Actually my Lumatek has a 110% setting too which I use deep in flowering.

awesome. thanks!

cool avatar btw.