Interpart Expressions are appending an apostrophe with a number

In the Expressions dialog, why do the expression names have appended an Apostrophe Number ('2)?

For example:

original_name'2

original_name'3

original_name'52

If the template (or seed part) has expressions, every time this template is used, the expressions are added to the file.

Every time the expressions are added to the file, the additional expressions are added with an appended suffix of an apostrophe and an index number: '2, '3, '4, etc.

For example, Create a drawing template that contains interpart expressions.

Now use the template with the interpart expressions to create a drawing.

The newly created drawing will have just the original interpart expressions with the original names (such as 'MONTH', 'YEAR'):

However, if this same template is used as a sheet template, insert 2 more sheets into this drawing.

Notice each time this template is added an additional time to this file by inserting sheets, the interpart expressions are added again from the template, but with the suffix '2, '3: