The calculations on the Totals Display can be configured by Administrators via Estimate Template settings.
The Package Totals display cycles through each of the available totals configured for the Estimate. Clicking the Package Totals hyperlink will reveal a list of each of the Package Totals in the Estimate. It can be closed by clicking the gray X that appears in the top right corner.
An example of the Totals Display and the Package Totals for an Estimate.