You have to think of it as making a decision once a candle has closed or on the fly while a candle is still forming.
If you have a 1 hour strategy that also looks at a daily candle then with ‘updateonclose’ it will only consider the values of the last closed daily candle and any indicator values etc of that last closed daily candle when it closed. With ‘default’ at the close of every hourly candle it will look and see what the current values are of the currently forming daily candle and use those values.
