The CalculateContamination description says:
Calculates the fraction of reads coming from cross-sample contamination, given results from GetPileupSummaries ... this tool estimates contamination based on the signal from ref reads at hom alt sites.
It produces a resulting contamination table that looks something like:
level contamination error
whole_bam 0.001012896128155539 1.8192151501912648E-4
I wasn't able to find an explanation of what the output actually is. Of course, I assume that "contamination" and "error" should be as close to 0 as possible, but what exactly are they? Is it contamination from potential other individuals based on population allele frequencies? What happens when there is a matched normal? Do they both need to be contaminated? What about contamination of the normal by the tumor? Those seem to be very different problems, but could both be labeled as contamination.