How to place the label for a guide in the middle of the lower and upper limits

[RobertBuckley1]

I have placed a guide in an arcgis online dashboard with an upper and lower limit and would like to display the label for this critical area left center. In the Dashboard settings I only have the option to place the label either outside or inside of the diagram and left or right. The height of the label within the Dashboard is fixed at a around 80% of the way up.

I have seen other dashboards where the label for these area between the upper and lower limits is centred. How do achieve this?