I am with Ed on this as something doesn't make sense with what you are saying???????
First the minisite is a grain focuser that you put your eye close to and at 10x you look for sharp grain and may not be able to see actual image. It should have a mirror that reflects the light that comes from the negative into the eyepiece. You are not looking at the baseboard.
The Magnasite that you lost is an image magnifier that you use by focusing the "image" at much lower magnification. It also allows you much more eye relief meaning you don't need to get as close as with the Minisite. I happen to use the Magnasite most of the time as I find it is easier.
To use the Minisite - First focus that line as described previously. Then project an image onto the baseboard or easel and rough focus it with the unaided eye. Then place the mirror part of the Minisite at a dark area in the center of the image and look through it to see what looks like grains of sand. Focus to get sharp grains of sand.
With my enlarger it is easier to focus on the grain with the lens stoped down several stops. At f2.8 it is so bright I sometimes have trouble seeing the grain especially with light negatives. At f8.0 it works well. Also with that unit you can't use it out at the edges of the projected image, it must be close to the middle or you will see nothing.
Hope this helps and isn't more basic than you needed. Just thought I'd cover all bases since you are used to the Magnasite.