Update PREVENT_STUCK_MODIFIERS documentation in README

README.md

@@ -115,8 +115,9 @@ If such situation bothers you add this to your `config.h`:
 
     #define PREVENT_STUCK_MODIFIERS
 
-Warning: This option uses up 1 byte of memory per key. For example on
-Planck it uses 4\*12=48 bytes.
+This option uses 5 bytes of memory per every 8 keys on the keyboard
+rounded up (5 bits per key). For example on Planck (48 keys) it uses
+(48/8)\*5 = 30 bytes.
 
 ### Remember: These are just aliases