SureCount offers two ways to count the symbols.  Auto-Count uses the symbol you assigned, compares the pixel arrangement of the symbol to the area selected and using the tolerances set on the Drawing Symbol dialog, marks the symbols that match.  The accuracy of the match depends in large part on the quality of the drawing and the tolerances set.  The electronic form of the drawings, especially scanned ones cannot be as exact as the originals. In some cases it will count symbols that should not be counted and miss some symbols that should be counted. When you use Auto-Count, you will want to visually check the drawing to ensure that all the correct symbols are marked.  

The Manual Count function is used both to mark symbols, counting them as you go and to remove marked symbols decrementing the count.  Manual count works as if you had a colored marker in your hand.  You will mark (click on) each symbol on the drawing that represents the item you are counting.  At the same time, SureCount increments the counter in the Object bar for that symbol documenting the total.  If you click a mark on the drawing, it acts like an eraser, removing the mark from the symbol and decrementing the total symbol count at the same time.