103744 Total users...good review??

hi guys this probably is the most easiest project u have ever come across.. i need some help with a file that shows total users on a phpbb based site.. BUT i want to show the last users ID (not username) now it shows # number of activated users i want # number -number being the last usersID so if activated are 4000 it still shows 8000 as 8000 might be the last users ID.. thx