This means that there will be no interference between the Global Variables of the same macro which is used in 2 DiaryGridLines, in the same Script. For example suppose you had a macro using ng1 to count the number of pages, being used both in a 5 pages and in another 12 page DiaryGridLine, of the same Script. At the end of the Script generation there would be 2 separate instances of ng1, one with value 5 and the other with value 12.
Similarly, within the same DiaryGridLine, if the same macro is used for 2 different macro indices (for example [1*1xxx] and [1*2xxx]), the value of ng1 stored for the token [1*1xxx] will be totally independent of the value of ng1 stored for the token [1*2xxx].
You can, however, share global variables between different macro tokens of the same DiaryGridLine, as long as they share the same macro index. We will see an example below.