As part of the launch of the new Azure App Service, all your existing web sites from Azure Web Sites are now migrated to Azure App Service plans. In my case, because I was running my web site on 2 Shared instances, it migrated each instance to a separate app service plan – Default 1 and Default 2 (there doesn’t seem to be any way to rename these plans at the moment).
In the old Azure portal, you can manually scale up or down the number of instances from 1 to 10 in Shared mode.
However, at least in Shared mode, this scaling up/down capability has now been removed – you are limited to a single instance.
However, if you go to the old portal (e.g. www.azure.com portal) you can still scale up or down and it works the same as before.