Strange temperatur calculation IMU3000

Hello,

The datasheet gives not a clear answer how to calculate the exact temperature. My question is:

is the temperature negative when I have & 0x8000 before or after dividing through 280 and adding the offset of 13200?
With other words: 2s complement shows me on the byte 15 if the value is positive or negative. Adding the offset and dividing through 280 will change it. So do I have first to divide through 280 and then check byte 15 or do I have to check byte 15 and then dividing.
Invensense would make it easier if they would write the 0°C value and another value, for example +25° and -25° in a binary format....