Check you pump gauge:

It does takes a little time to fully inflate your board. It can seem like it takes forever when you first start out but we encourage you to keep pumping! The gauge will register at 7-8 PSI and the act of pumping will get harder. I have to use my whole body when I get up to 12 - 15 PSI. It is highly unlikely that you will over-inflate your board with a hand pump. 

This article give some helpful steps:

If your pump gauge has a clear sticker over the face of the gauge, please do not remove this sticker! It is designed to protect the face of the gauge and removing it will cause the face of the gauge to be unreadable