The Altitude Factor calculation is given on the CRaTER algorithms pages, under the "Dose Rates" tab. The relevant page doesn't have a unique URL, so...
Removing the altitude correction simply shifts the reading back to about 100km above the moon's surface, the altitude of LRO's orbit. This shows the...
And, still on the topic of secondary radiation, we know that the Apollo dosimeters had a fairly limited detection range for neutrons. Another reason...