On Instrumentation page you set defaults for various items relevant to the instrumentation process.
Marker style
GpProfile uses markers to mark instrumented code in the program so it can be safely uninstrumented later. Default marker style is {>>GpProfile}, which you can change to {$IFDEF GpProfile}. If you use the second option don't forget to manually $DEFINE GpProfile in all units you want to profile.
Compiler version
Here you can select default Delphi environment if you have more than one Delphi installed.
Speed/Size
Profile files get pretty big (you'll reach gigabyte sizes without a problem) and sometimes you'll want to keep them smaller at the expense of target program speed. Beside uncompressed data, GpProfile supports two levels of compression.
Show all folders
Check if you want every new project to show all used units, not only units in the project folder.
Start profiling on target startup
When you want to measure just some part of the program, you must disable profiling autostart with this option and start/stop profiling manually by using API calls.