Ok. I get it now.
You'll need to launch regedit.
Navigate to HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics
Locate keys: IconSpacing and IconVerticalSpacing
Write down those values (in case you need to change them back).
Change values of those keys to: -1125
Sign out from your windows profile (don't confuse it with just locking the screen).
Login back and change size of screen icons to small and back to medium.