Trust sells property. Why if the distribution is done as a % there is no cap gain on the K-1, but if distribution is specific amount there is a cap gain on the K-1?

"Why if the distribution is done as a % there is no cap gain on the K-1...?"

That is sort of a quirk in the program which happens occasionally (and randomly). 

You can almost always get the distribution to flow through to the K-1(s) when entering a distribution amount but distribution percentages sometimes fail initially.