The number of the patches is from normal to tangent, looping over Thetas
and Azimuths... I think it is easier for you to see it instead of reading
it. You can go to http://www.radiance-online.org/download-install and
download the BSDF viewer, and put Show Patch Numbers.
About the units, I understand they are Incident Irradiance over Outgoing
Radiance, and the number there can be deduced as the percentage of
transmission of that transmitted by an "air" layer. In the case of Klems
(W6 standard) basis, the values for the air layer are, aproximately:
*Patch Number* *1/cos(Θ).Ω* 1 41,9043 2-9 42,8764 10-25 45,6281 26-45
42,333 46-69 44,6724 70-93 44,6724 94-117 50,7996 118-133 45,6281
The experts may have much more information about this.
This question probably belongs on the radiance-dev list, so I am cross-posting there and ask you to sign up (if you haven't already) and respond on that list. (Same goes for others -- thanks!)
The data order in the file is a matrix running from smallest to largest Klems patches, with the columns (inner loop data) corresponding to the input directions. This is verified by a tag in the "DataDefinition" section that says: