Beast Output Negative and Large Values?

Hi folks
For some strange reasons, I am trying to manually convert Beast output to 8-bit RGBM.
Using Python OpenEXR, I find:
max(channels[0]) == 290.000061456
min(channels[0]) == -0.00781250557338

290 seems oddly high, and outside of RGBM max range (8.0f). Does unity clamp these values at some point?
With light intensities only in [0..8], and colors in a 0-1 range, How am I getting negative results in my lightmap?

Thanks!
Alex Mouton

 

Just to follow up, I had a Half to float conversion error.
The correct max was ~3.78,
The minimum is -1.0, which I guess is a signal for pixels that are unset in the lightmap.