Hi Panagiotis,
The Plots tab shows a standard box and whiskers plot. I am assuming the whiskers are the gray error bars you are referring to.
In our boxplots, the box indicates the median, 75th and 25th percentile. The whiskers indicate the max (or min) point within the IQR.
IQR is Q3-Q1.
Min whisker is Q1-1.5*IQR
Max whisker is Q3+1.5*IQR
regards
Jag