If you have a Garmin Forerunner, it relies on satellite info to calculate elevation and grade percentages. These are not accurate. I have done rides where the total elevation climbing was 4500 ft and my Garmin Forerunner has come up with almost twice that. If you have the Edge, it has an altimeter built in to it and may be more accurate for straight elevation numbers but again I'm not sure if it calculates grade based on rise over run or from satellite info.

Looks steep though and good on ya!