Measure Pump Flow issue

I am trying to measure my pool pump flow. I am using an INTELLIFLO® VARIABLE SPEED pump. I tried to calculate it using the pressure gauge, and vaccum gauge which I installed on the pump. Here are my readings:

On speed 2350 rpm, I have 10 Hg, and 20 psi. When I use the folowing formula to calculate the flow

TDH = Vaccum reading * 1.13 + pressure reading * 2.31, I get 57.5 for TDH

The problem is that 57.5 feet for TDH does not make much sesne by looking at my pump performance curve for 2350 rpm, which I have attached. My pump flow look pretty fine, and the pump seems to be doing pretty good filtering.

Can someone help me understand what I am doing wrong?

Afshin - Are you getting the pressure reading from the gauge at the filter or are you getting it from the pump? The pressure reading should come from the gauge on the pressure side of the pump.

The reading is from the pump, not the filter.