Stock Status not working correctly?

Hello, thank you for the plugin. I have been trying to add PHP code to my child’s function but nothing seems to be working. I have installed your plugin and after playing with the settings I was able to get “in stock” to read “Classes Available”. Here’s the issue, If I select “manage stock” the only setting that allows the text to be changed is “%s in stock”. No other setting changes anything… Please advise, thank you.