Not really. It works like so using your situation:
SM's roll 2d6 and add them together for a charge range. They get a 5 total.
They started 12" away, and their charge distance is 5", so they are short by 7", but since they couldn't make the charge, they remain exactly where they were before the charge range dice were rolled, so at the end of the assault phase nothing has happened other than some dice rolling, no models are moved.
However, I believe Overwatch happens right after an assault is declared but before dice are rolled (Someone correct me if that is wrong), so there is that to mess with things.
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