Shock Pump question

[Heel Drop]

So I got a shock pump today and I am wondering......

 

the pump inlet screws onto the valve and then a second knob must be turned to open the valve and let the air in.( Its liek a little secondary turning knob that has a pin that opens the valve)

 

I pump it see the pressure but then when I undo the knob to stop the air from going in/coming out I hear a little air escape.

 

Because the air pressure is so high I wonder if when I read the pressure this air that escapes contirbutes to that reading and that means when I undo the knob and I hear air going out the actual reading is then less.

 

When I use the air outlet knob its so sensative you just touch it and the PSI drops by 10-20 psi . I am just wondering when I read is it really that accurate once I undo the pump .If a little air escapes the reading drops

 

 

Any case that is what logic tells me.

[Heel Drop]

I acutally found the answer on a website its the air in the pump that I hear escaping not the shock air so its not an issue