Gerber output justification is based on the extents of each gerber file, so when you use Bottom Left, it could be different for every layer. The exception is when you use the Offset justification. The offset is based on the Board origin, and it needs to be the same for every layer, including the drill file, in order to align all of the files. It also should be large enough to place all of the gerber files in the positive quadrant.
So when looking at your PCB, zoom out so you can see everything, and place your cursor so it's below and to the left of those extents. That is the minimum offset you need. Round up to whole numbers to make it easier to enter, since you need to do that for every CAM file. So if the cursor is at -1300 mils for X and -2400 mils for Y, use 2000 and 3000 for the offsets.