"0 ms" is a real value; it means that whatever is being measured happened in less than 1 ms.
If no metric is collected, the value will show as "n/a". If there is no connection also "n/a" is shown as no data was collected.
The issue of large scale has to do with the visual presentation of the chart. The chart showed some extremely large values as well as some very small values, since the bar height is proportional to the value. The small values' bar cannot be seen at the default zoom level, for example if the largest plotted value is 3 minutes and the smallest is 2 ms, the plotted bar for the 2 ms will be too small to be seen at the default zoom level, it will appear as the 2 ms value has no bar. Zoom into it and the bar appears.