My monthly royalty statement often has corrections to earlier royalty statements, often many years in the past. For example, in a given month's statement there may be as many as 10 or 12 monthly corrections to earlier royalty monthly amounts for a single gas well. There are two entries for an earlier month with one entry deducting whatever the royalty was in the earlier month and a second entry with a new, I guess corrected, royalty amount. The difference is usually a few dollars up or down. Does anyone know why corrections would be made to royalty payments from several years ago?