You need to measure the height of the fork oil from the top, with the spring out and the fork compressed. You can't guarantee that all of the old oil drained out, so 475cc might be too much. And I'm sorry that I don't have the measurement for you.
I looked up the numbers and got 457 ml instead of 475. Ducati supposedly increased that spec by 30 ml to 487 to improve performance. I don't know if the spec'd oil level is for the lower or higher amount. Oil level for the Showa GD041 that should be on the 94 M900 is 79.5mm from the top; spring removed and fork fully compressed. If you overfill it, you'll know when you lower the spring and spacer back into the oil ;D
If it is the Marzocchi forks, it will be different.
Like Scott said, measuring is the way to go. I changed the oil in my non-adjustables (95 M900) back around October/November and had to adjust the oil levels a little bit after pouring in the measured amount.