A line over expressions

Here $abcd,efgh$ are numbers and not the products of $a,b,c,d,e,f,g,h$ For satisfying the condition given in the question we need to max. out $abcd$ and minimize $efgh.$ For maxing out $abcd$ we need its digits to be the maximum from $1---9.$ Thus $abcd=9876$ and for minimizing $efgh$ we need its digits to be the least but we can't take $e=0$ because then $efgh$ wouldn't be a 4-digit number.Thus, $e=1$ and $f=0,g=2,h=3$ Thus,max. difference $=9876-1023=8853.$ BTW this is a highly overrated question.