How much diff. oil?

I just purchased my 2002 Honda foreman 450 about 4 months ago. It only had 47 miles on it when I got it and had never been in any mud. I now have 320 miles on it, and I am going to change the motor oil, filter, and change the oil in both diffs. The question I have is, How much oil does the diffs hold. The original owner lost the owners manuel and the guy at the Honda shop gave me a bottle for each diff, but the bottles only have 8oz. in them. Is 8 oz enough for each diff? Also how much oil will the motor hold, because he gave me 4qts and the filter.
This bike had never been of the guys farm. He used it mainly to mow his yard with. There was no mud no where on the bike. The reason he sold it was he took his granddaughter for a ride and stood it up going up a hill on his farm. It scared him so, he was selling it to buy a side by side. I got it for only $3,700. It still had the honda promotional sticker on the left front fender that stated that Honda would pay $100 for you to test ride this vehicle. He also stated that it had never been washed, there was only minimal dust on this bike and all of the grease pencil markers were still on it. The tires also showed no signs of wear on them either, but that has changed.