Soulver supports "Resume" feature which is built into macOS, so that your open sheets, with their sizes and positions, are saved automatically across launches.
Please ensure that
Close windows when quitting an app is NOT enabled in your macOS
General system preferences pane:
By default Soulver formats your answers with SI notation:
To disable this feature go to the
Line menu >
Display With >
Notation for Large/Small Numbers and untick the menu item.
To turn off notation for lines by default, go to
Edit > Tweak Engine > Answers