Math
OK I have not been quilting for a few months and my brain is getting fried with a mental block. If I am creating a square that I want to measure 2 inches finished, and I want it to consist of a light and dark half square triangle, why am I adding 3/8 inch to each square cut. To me it seems like if I have 1/4 inch seam I should add 1/4 inch. Now I understood this before but now I am just coming up blank so please help. Thank you