I installed the new oil seal today and think I did a good job. But not sure if it's all the way in. I hammered it in very carefully using a matching socket untill it was flush with the axle then it didn't seem like it would go any farther even with some harder hits so I left it like that but according to my measurements that means there might still be a small space between the seal and bearing, and not sure if I heard that its supposed to be pressed all the way till it hits the bearing in which case it would go deeper than just being flush with the axle.
I used my own judment but without experience that doesn't cut it

 

the 5 or 6 that I've done have all been flush and never had a problem. As long as the axle shaft had no burrs, rust, etc you should be fine.