Dyno correction of 27% is not valid. Anything above/below 7% is invalid according to SAE J1349 horsepower correction specifications.
The weather station on the dyno is broken. You area reading ambient pressure of 24.14 inHg (817.14 mBar). That measurement is not possible on earth. Lowest pressure ever recorded on earth was 25.69 inHg (870 mBar). "Normal" pressure on earth is 29.92 inHg (1013 mBar). So you can see 24.14 inHg isn't possible and the weather station on the dyno needs to be fixed/replaced.
That explains the corrected results but not the uncorrected results. Frankly I wouldn't trust this dyno and would go somewhere else.
Ignore the suggestion to dyno in 5th gear even though it's 1:1. The suggestion is rooted in the myth that 5th gear has less drive train loss. In this transmission, it's actually the second least efficient gear. So if you dyno in 5th, you will probably see even lower results. Search the forums as this has been discussed a few times.
Here's a link to the dyno database where you can see about 500 dyno results for the m3. There's a quick link to show you all "stock" cars so you can see how yours compares.
http://www.rcollins.org/bimmertech/DynoDB.php
Good luck.