If you are a member of a basic site (a non-paying member), the limit of people that can be entered in the tree is 250 and the limit of storage space is 250 MB. This includes all family trees on the site, whether they were created online or in Family Tree Builder and published to the site afterward.
If you would like to upgrade your account, open a browser, go to MyHeritage.com and make sure you are logged in. Then go to your Family Site. Once at your site, look for the upgrade banner at the top left corner of your home page or mouse over your name in the upper right corner of the screen and select “Site Settings”.