No, he spelled "their" correctly.
Now write out 500 times: "There is a difference in spelling and grammar".
"Their" denotes ownership - for example, "it is 'their' car.
Still don't understand the difference in spelling and grammar! Probably never will.
Now write out 2500 times:
"The Doctor is in and is always correct"!
(put you in a pickle, huh?)
We could do this all night............!