Add description text to info button in bar chart

The bar chart below shows differences in the composition of the water inside and outside the region of interest (ROI) separately for each parameter. By clicking on a bar, the exact value of the deviation is given.

This analysis helps to gather information on whether the chosen region of interest actually contains an anomaly, i.e., is the water in- and outside the ROI composed differently? It also supports deciding what kind of anomaly has been found, i.e. in which parameters is the difference visible and how does its value deviate from the water outside the ROI?

For each parameter, the ratios between the mean value of data inside the region of interest (ROI) and outside of it (NROI) are calculated. The deviation from a state where both waterbodies are composed similarly is then shown in the bar chart below. It is calculated as:

Ratio(param)=((Mean_ROI (param))/(Mean_NROI (param))*100)-100

I'd like to hear your comments, especially on whether it is comprehensible :)