From my understanding (someone will correct if I'm wrong).
The day you start doesn't count and neither do weekend /holidays.
So by starting the procees on wed. 3/14.
thur 3/15 counts as day one
fri 3/16 counts as day two
neither sat 3/17 nor Sun 3/18 count towards the 72 hrs.
so that would make mon 3/19 day three but I pressume Bob's is closed
That would mean 3/20.. they are probably just trying to cover themselves and have you come back after the 72hr has offically expired, they may or may not call before if the approval comes in early.