You must have heard "nought", a mainly British name for the "zero" digit. It rhymes with caught, ought, etc. "Nought point five" is a typically British way of saying aloud what is written as "0.5". In figures, you write one million as a one followed by six noughts. British people sometimes refer to the decade that started in 2000 as 'the noughties'.
number (ZERO) [ C ]
mainly UK (USA usually naught) the number 0 or
He said it was only worth £10, but really you could add a couple of
noughts to that (= it is really worth £1,000).
Nought (Cambridge Dictionary)