"Cò mheud an-diugh? Ceithir deug."
Translation:How many today? Fourteen.
It's actually just a standardisation thing. According to the Gaelic Orthographic Convention, cia mheud is the spelling that ought to be used. As for why both ways are taught on the course - it was an accident. The course had been released before we noticed :) We have got rid of cò mheud in Tree 2.