Is there something wrong with my turbo boost testing?

[springbeauty196]

hi all. Ihave a 3rd gen Colorado and i have recently bought a gauge to measure the turbo boost on it. i paid additional for high programming but this gauge on reads 20 psi, when it should be at around 27. 

am I doing something wrong with this? any help will be appreciated

 

[slushy08]

maybe its end point is set at 20? honestly its really hard to depend on these tools, better drive it and feel it yourself, if youre not too satisfied then maybe have it tuned.