When you upgrade your package, you pay the price difference to receive the additional number of resources and the additional number of months' access.
For example, if you upgrade from a PTE Silver to a PTE Gold, you will pay USD$90 and receive an additional 3 writing assessments, 3 speaking assessments, and 1 tutorial. You will also get an additional 3 months' access.
To compare packages, see our website.
If you have any questions about the validity of your package, see this article: How long is my package valid for?
If you still have questions you can also email us at email@example.com.