When purchasing a template it creates a new project with all the pages in the template. This project then can be customised to create your new website. Template purchase is a single use licence so it is intended for just the one project.
Please note that if you are on a free Webflow Starter account plan, and your templated project does not have a Site plan added, then the project will be limited to 2 pages only. You can still access all the pages in the paid template (unless deleted) however will not be able to duplicate a page, or add a new page without upgrading your account plan, or adding a site plan to the project.
So it is generally better to customise the existing pages in the template if you do not wish to add a site hosting plan yet.
If you are getting a page limit error after adding a site plan (hosting) to that project, or have any additional questions about page limits, please reach out to Webflow support on our contact page at Webflow Customer Support | Webflow University, so we can help to check further.
Note that as Jeff mentioned above, the 100 static page limit is currently a hard limit and cannot be increased. For more information on page limits please see Pages panel overview | Webflow University.