From the ATP site
Q. What happens if two or more players are tied?
A. When two or more players have the same total number of points, ties shall be broken as follows:
(i) the most total points from the Grand Slams, ATP Masters Series Tournaments and Tennis Masters Cup, and if still tied, then,
(ii) the fewest events played, counting all missed Grand Slams, ATP Masters Series Tournaments and Tennis Masters Cup they could have played (as described under 1. above) as if played, and if still tied, then,
(iii) the highest number of points from one single Tournament, then, if needed, the second highest, and so on.
SO yeah I guess Hewitt has more points from TMS and Slams.