This could be reproduced on version 4.0.0b10 (0a7760ba81f3). When changing the rolloffMode from Custom to Logarithmic on the animation curve, the final node jumps up to 0,2.

To reproduce:
- Open the attached project
- Load the scene "AudioTest"
- Select the Main Camera in Hierarchy View
- In Inspector > Observe that the Volume Rolloff is set to "Custom Rolloff" and that the final node is at 0.
- Observe also that the min. distance is set to 1 and the max. distance is set to 5.
- Now change to the Logarithmic Rolloff mode and observe that the first and final node changes positions.

Expected result: As a user I would expect the nodes to stay at the same positions/values whether user is using the Custom or Logarithmic Rolloff modes.

Please see attached screen shots for further details.