I don't know what is modeled in the foreground system and which uncertainty is entered in the foreground system by the user. But looking at the distribution and the confidence intervals, the values for the distribution look very reasonable, having 213 mean, 192 sigma, -99 5% CI, 521 95% CI, median 210. You can also export the data and do the statistics yourself.
If you think that the values are not what you expect, I would try to find the reason behind inside the uncertainty that is individually set in the exchanges and I assume that the reason behind is not the calculation procedure or the statistics calculation itself.
It seems like you have a very broad uncertainty distribution, so maybe you used large uncertainty values inside your exchanges. Be aware that for Gaussian distributions you enter the standard deviation of a Gaussian distribution into the exchange uncertainty, and for Log-normal distributions you enter the geometric standard deviation for a log-normal distribution into your exchanges (which is also written in the uncertainty box).