kilomtres and kilomtres behind是什么意思

出自一个英文笑话
Mr Brown is one of my friends.He can run very fast（快）and likes to show people how fast he can run.
One day,a thief（小偷）got into his house,took some of his things and ran out of the house fast.Mr Brown found it and ran after him,and shouted（喊）,"Hey（嘿）!Don't you know you can't get away from（逃脱）me?"
But the thief ran much faster.Mr Brown got angry（生气的、发怒的）and ran faster,too.He was soon a few kilometres away from his house,he was running hard when he met me."Why are you running so fast?" I asked."I want to catch a thief," said Mr Brown."But where is the thief?" I asked."【Kilometres and kilometres behind】." said Mr Brown proudly,"He thought he could run faster than me,but you see he is wrong."
Kilometres and kilometres behind
==落后我好多好多公里呢