http://www.thehinkymeter.com/casey-anthony-murder-trial/timeline-and-discovery/
In this article it was explained that not only was this one allele coming in under a generally accepted range to be used in court, and could not be properly called DNA, but there was a potential backfire to the defense touting this as coming from a stranger. The problem was that the DNA results from Brian Burners shovel showed a mixture of individuals that also came in under generally accepted levels. This mixture contains alleles (more than one, by the way) of what appears to be a male and female. It contains alleles (several) that are common to Caylees DNA results (both from the tibia and Jesse Grunds paternity test results) as well as what appears to be Brian Burners DNA which is no surprise since its his darned shovel! Brian Burner has a 17 allele in the D3S1358 loci just like the shadow 17 allele on Q64-2 test result of a piece of the duct tape on Caylees skull. The point being that if the defense was silly enough to take less than a human cell of a generally unacceptable test result on this one allele, they would open the door to the state showing the possible connections between Caylees DNA, Brian Burners DNA, and the shovel Casey borrowed in the week of Caylees death (and most likely disposal).
I think this is significant.