How far in should the oil dipstick tube go?

I have a lot of oil built up around the base of my oil dipstick tube. There is a flange about 1" above where the tube goes into the block. Should that flange be the one to seat in the block or is there another flange near the bottom of the tube?

There are two flanges. Sometimes the tubes fit kinda loose especially if the bracket is not attached to the manifold.