From Ascgroup

Average Resolution Time shows the time it takes for the resolution of CAs. It plots both the average duration of the open CA (left Y-axis) and indicates the number of open issues (right Y-axis) as a function of time (X-axis).

The above chart shows for the period of time in the middle part of the time duration there were few issues but they required considerable time to bring to resolution, while in the last three months of the period indicates that issues were resolved more quickly than in the three month period in the early part of the graph (July – Sept).