README.md in strong_migrations-1.4.2 vs README.md in strong_migrations-1.4.3

- old
+ new

@@ -222,10 +222,10 @@
 
 And some in MySQL and MariaDB:
 
 Type | Safe Changes
 --- | ---
-`string` | Increasing `:limit` from under 255 up to 255, increasing `:limit` from over 255 to the max
+`string` | Increasing `:limit` from under 63 up to 63, increasing `:limit` from over 63 to the max (the threshold may be different if using an encoding other than `utf8mb4`)
 
 #### Good
 
 A safer approach is to:
 