The start count can be changed if the set button is pressed before countdown. Each digit is lit in turn, incrementing from zero until the set button is pressed again. There are 15 settable start counts. You cycle through them using the select pushbutton. The set button changes only the starting count presently displayed.
Labels start in the first column.
Both the equates and destination lines have labels attached to them. Everything else starts in column 2 or beyond. ASM', you will get a number of warnings and messages. Ignore them, it's the easiest way to set up these registers. There are two routine going on at the same time.