Newbie Question re: Wharton Unit in Gaines County

I’m really new at this so please excuse the stupid question.

I inherited royalty interests from my mother and I found a Royalty Deed that says E/2 NE/4, Sec 10, Blk. A-23, PSL Survey, Wharton Unit. Her interest was .00415906. Divided by 3 my interest should be .001386. I haven’t received a check in a long time but got one today from Sabinal for .00000768. Can anyone tell me how to sort this all out?

Most likely the interest is being reduced on the basis of tract participation in the unit. For example, if you own a .015 interest in the NW/4 of Section 1 but the NW/4 only comprises 10% of the total unit acreage then your interest would be reduced to .0015 (being .015 * .1 = .0015). A division order analyst should be able to explain exactly how they are breaking down your interest if you contact the oil company operating the unit.