The command line option --vacuum rebuilds the indices of SpiderOak ONE's local database and in so doing reclaims disk space. This is periodically performed automatically in the background, so it is generally not needed to run this command manually. Still, you may use it to perform a manual cleanup if you wish. Here's how:
First, quit SpiderOak ONE. Don't just minimize the application, shut it down completely.
Open a command prompt window or terminal. Enter the appropriate command from below, all on one line, then press enter:
cmd /c "C:\Program Files\SpiderOakONE\SpiderOakONE.exe" --vacuum
Let it run. Be patient: it may take a while before output is displayed on the terminal. When finished, relaunch SpiderOak ONE.