Props to you for being the first person who actually explained what the statement meant as opposed to others who just got very defensive and said things to effect of "it's your own fault for being too dumb to understand" whenever someone expressed confusion.
Perhaps, these people should have asked why it was possible, so they could become educated.
It is really just basic percentage calculation.
Apple reduced revenue by $5 billions. If Greater China revenue is reduced by $6 billion, it would constitute 6/5 = 120% av the reduction of the revenue.