The zero point (0|0) of the grid coordinate system is the upper right corner of the desktop (either with or without menubar - depends on your settings in System Preferences > General > Automatically hide and show menubar).
With a fixed grid size progressing to the left and the bottom of the desktop you usually will get gaps (=incomplete grid boxes) at the left and at the bottom.
Example with your screenshot:
Each box has a fixed size (pixel x pixel) depending on the grid spacing setting. The leftmost column is incomplete and the bottom row is overlapped by the dock. Both usually won't be used to place items in there.
AFAIR Windows uses a relative grid size and a natural number (=positive integer) of tiles (in the x- and y-direction).
Assuming the grid spacing is in pixel (or better some natural multiple), you can set it to a whole integer divisor of your monitor size. I think 60 will fit a lot of common sizes:
/usr/libexec/PlistBuddy -c "Set :DesktopViewSettings:IconViewSettings:gridSpacing 60" ~/Library/Preferences/com.apple.finder.plist
Check the settings with:
/usr/libexec/PlistBuddy -c "Print :DesktopViewSettings:IconViewSettings:gridSpacing" ~/Library/Preferences/com.apple.finder.plist