Good to know it works for you. But it's not QlikView's fault but that's natural behaviour in programming paradigm. The reason for this behaviour is the nature of the operators used in the expression and the order of precedence. I would recommend you to read - The Order of Precedence of arthimetic operators for clear understanding. However, Let me try to explain:
Above expression won't work without the brackets (in red colour) because we are using "+"/addition arthimetic operator and when we use the brackets then QlikView aggregates the both the count values and then adds them together. So if there are no brackets the expression evaulation might be confusing with the string concatenation operator and it returns a NULL value.
However, below expression works without the same brackets when we use the "*"/multiplier arthimetic operator because this operator take first precedence when we don't specify any brackets.
