Viewing a transaction and not saving changes to it won't modify the date or the last user to change the transaction. That requires an actual change.

So, not sure what you're seeing / why it says the Admin changed the transactions if you (the admin) didn't.  You can use the Audit Trail report to see the current and past versions of a transaction, and in many cases see the change, if it's tracked (not all changes are).

Notably, changes that are tracked include fields that aren't on by default on the report; You can modify the report and add more columns for fields that might have been changed.