SSIS Package Duration is big before it begins executing
I think it's hard to predict where those 2 extra seconds are coming from without seeing your SSIS Package and how you're running it. A rough guess is it's some additional runtime that added up from starting the package execution + starting execution of each step. I wouldn't worry much about it unless you start seeing huge discrepancies (but if it's consistently off by a few seconds, then I would lean to what I previously guessed).
According to this StackOverflow, those reports aren't the most accurate way to track and analyze execution times too: SSIS job taking 'hours' -- All Executions report not adding up or showing errors -- where to find cause?
Specifically see Nick.McDermaid's comments:

Everything you need should be in the logs / reports. No need to run it locally. It's a
pain, introduces network traffic, is not a true representation and
doesn't give you much more information. There is a package 'total run
time' in the top level report (displayed in seconds).

Here are some alternative ways you can track SSIS Package execution times: Tracking Execution Times for SSIS Packages