The Performance % Complete field in P6 is utilized for Earned Value (EV) calculation and provides the percentage of the planned work that is currently completed. It serves as the initial field to assess the progress of an activity or project.

In Primavera P6, the Performance Percent Complete calculation technique is defined at the WBS level. 
Define which technique to use by going to Project, WBS, then selecting the Earned Value tab. This article do not explain how summary (rolled-up) performance % complete is calculated. It is discussed at this article:Why Performance % Complete doesn't roll up in Primavera P6?

The Schedule % Complete in Primavera P6 specifies how much of the activity's baseline duration has been completed so far. Computed based on where the current data date falls between the activity's baseline start and finish dates.

How do you read the status of this activity? It looks like blue actual bar is not truly representing activity progress as it is more than 20% of total bar length.

As some of the project data within XER export files are part of global metadata or dictionaries, users need to be cautious when importing XER files coming from a subcontractor or client. XER files may include codes, calendars or resources with IDs/names same as the ones in your database.

In order to make sure that imported data is not colliding and overwriting with your global data, import process can be configured to add everything in the export files as new records.

Primavera Unifier OpenOffice Extension is a tool for Unifier Administrators to fetch, create and update Unifier BP records. Here is the Unifier OpenOffice Extension Installation Guide.