Can't edit legend text when using High to Low symbology

[HelenCooper]

Hi all, 

I'm trying to edit the legend text on a webmap, where I'm symbolising by counts and amounts, and then using the 'high to low' theme (see screenshot below). 

I'm sure it used to be possible to click on the numbers that are underlined, and add additional text (to give a more descriptive legend) but that no longer seems to work.  

Any suggestions would be gratefully received!

Helen