What they did was part of an orthostatic BP check. For everyone, BP will be highest when lying down, a bit lower when sitting, and lowest when standing. When there are significant differences between BPs taken in these three postions, then a problem can be indicated. The diffence in yours is negligible/typical.
Some types of medications, dehydration, low sodium, and lots of other conditions can cause sometimes BIG differences between orthostatic readings.When some one presents with for instance an episode of suddenly feeling dizzy or fainting, checking orthostatics would be important. It doesn't diagnose anything, just gives data for further investigation. The "why" must still be ferreted out. Sometimes the "why" is very simple and sometimes it is related to a serious disease process.
And then there are people like me who run a 90/60 BP and sometimes the dyastolic is even lower. This is my lifetime norm. The only issue is rare orthostatic hypotension if I bolt out of bed too fast in the am, or get dehydrated.
Everything is relative to the individual, even given norms.
From where I sit, you have a great BP. Do a happy dance!
As some others asked, I'd be asking: What are they selling....?