Electrical Repair Questions? Ask an Electrician for Answers ASAP
 The ceiling box has only two wires, black and white.
 The Lighting fixture (Lithonia 198 URJ you can see the specs at homedepot.com or the Lithonia website) has THREE WIRES (plus a Green GROUND). RED, Black, and WHITE.
 This garage light is controlled by 2 light switches.
 Yes I have a volt meter with probes.
I have not yet wired up the fixture nor hung it, awaiting figuring out how to do it!! There are no helpful instructions in the box (unusual for Home Depot).
Sorry, there is another number on the box too =-= which must be the part. It has 6 lights. Part Number is XXXXX
The Home Depot Link is: http://www.homedepot.com/p/Lithonia-Lighting-Industrial-6-Light-High-Bay-Grey-Hanging-Fixture-IB-632-MVH/202193185#.UjYZGdJOPTo
I believe it is a single ballast set-up. I will have to disassemble the fixture in order to view the ballast.
Here is information I copied from the Home Depot website I directed you to:
I am pretty sure it is a single ballast. The fact that it is a multivolt 120-277 Volt may suggest that the RED wire is for a 220 connection? Does that make any sense. I don't want to waste your time, so if you don't have any other information I will dis-assemble the fixture and see if there is a wiring diagram on the ballast -- and confirm it is indeed a single.
Nope -- It is red. I am going to go and dis-assemble the light fixture now to see what I can find out from inside. I can then snap a picture if necessary, and then I will try to send it to you.
Will take a few minutes.
Not sure how to send you a picture, but opening the unit I found the answer -- now I just have to put it all back together. Once apart, there are 3 wires that feed the connector that leads outside BLACK, WHITE, and GRAY. The GRAY TURNS TO RED on the other side of the connector. The label indicates:
Line Voltage Dimming Control
Gray Wire Connected to Line or Neutral: operates at 100% Light Level
Open Circuit Gray wire - Ballast Starts At High Level And Dims To Low Level (60%),
It is a single Ballast -- Product Code 71497 -- A GE Ultramax T-8 Ballast.
I am just going to wire the "RED" (aka Gray) to NEUTRAL WHITE -- and then Black to Black and White White and it seems it should all work out.
Sorry this was such a tough one, and no information on-line. Now I have to go back an put the fixture back together so that I can wire and hang it!!