Sitemap error

I got this error in my sitemap plug in.
# The last run didn’t finish! Maybe you can raise the memory or time limit for PHP scripts. Learn more
# The last known memory usage of the script was 25.25MB, the limit of your server is 256M.
# The last known execution time of the script was 3.63 seconds, the limit of your server is 120 seconds.
# The script stopped around post number 3878 (+/- 100)