Diff in RTF custom report

Summary:

We are trying to difference in two columns in RTF but not getting desired result. Answer should be 0

Content (please ensure you mask any confidential information):

Syntax used in Advanced:

Syntax 1

<?(_SOURCESYSTEMBALANCES_)?>-<?(_SUBSYSTEMBALANCES_)?>

result is --3338167.94-3338167.94(both amount is negative)

Option2

Syntax 2

<?(_SOURCESYSTEMBALANCES_)-(_SUBSYSTEMBALANCES_)?>

Result is blank

Version (include the version you are using, if applicable):

Can you please help us know how syntax to get diff in RTF template?

Code Snippet (add any code snippets that support your topic, if applicable):