okay I recently bought a phantom two and this is my setup.

Phanton 2
Immersion rc 5.8ghz 600mw tx
Spiro antennas
One patch antenna on FPV black pear
H3-3d gimbal. Hero 4 camera
Dji ground station
Iosd


right so my question is I am charging my battery 100%
Then  I am counting how long it lasts in the air to about 30-25%

I'm getting around 13 minutes max.  
On the software it has been discharged six times
I am basically hovering  going left and right not doing nothing too hard.  
I live in the UK the temperature is 11° slightly windy.  
Now I have never owned a phantom before Are these flight times less than they should be? Has the company sold me a dud product

Cold weather and wind will affect flight times.  Your time to 30% or so is not that out of line.  I get 15 to 17 minutes with 15 to 20% remaining at 60°F and up in calm conditions, for P2V+.

Optimal time listed in ads is most likely a bare phantom with no camera or WiFi unit, probably hovering a foot off the floor inside a building.

Most of my electric planes and helicopters only get 8 to 12 minutes, so the Phantom actually has better flight time than most electric aircraft I've been around.

mild weather and no wind, i get about 20 mins with my p2v
cold weather and moderate wind, i get about 15 mins maybe less depending upon how cold and how windy.  

i notice i burn just as much power holding in gps mode vs wind as i do compared to the cold temp factor, then again, the coldest ive flown is around 5-7C.