78 by 78 construction and 60 by 60 construction tells you how many threads are in your warp and weft per inch. This gives you a 156 (give or take a thread) thread count on the 78 by 78, and a 120 thread count on the 60 by 60. The 78(156) will give you finer stitching when handquilting, and generally speaking a slight less shrinkage.