Spectra Precision Survey Pro v4.5 Ranger Reference Manual - Manual (Page 97)

Job Menu
R-89
Recover Wasted Space Now : As you add and remove points and lines
in a job, empty gaps can result within the job file. These gaps use
storage space. This button will remove any gaps in the job file, thus
recovering the wasted space.
Note: Survey Pro checks for low memory situations every minute.
When the available system memory falls below 256K of RAM, a
warning is displayed.