fix typo

@@ -152,7 +152,7 @@ make.edges.mas_equalTo(UIEdgeInsetsMake(10, 0, 10, 0));
 make.left.mas_equalTo(view).mas_offset(UIEdgeInsetsMake(10, 0, 10, 0));
 ```
 
-By default, macros which support [autoboxing](https://en.wikipedia.org/wiki/Autoboxing#Autoboxing) are prefixed with `mas_`. Unprefixed versions are available by defining `MAS_SHORTHAND_GLOBAL` before importing Masonry.
+By default, macros which support [autoboxing](https://en.wikipedia.org/wiki/Autoboxing#Autoboxing) are prefixed with `mas_`. Unprefixed versions are available by defining `MAS_SHORTHAND_GLOBALS` before importing Masonry.
 
 #### 4. NSArray