So I recently ran into an issue where the droplet created did not match the size requested. I submitted a ticket and got the reasoning. Currently if for some reason the server requested can't be built it defaults to a 20GB machine. Since we currently can't resize the disk this is a problem.
First, if you can't provision the correct machine the best response is to fail the build and let us know. I had no idea from the admin panel that there was any issue. My droplet showed its requested size. Only by hopping on the server and running df did we see the issue. You can waste our time or lead us to serious problems down the road if we're not aware. Failing the provisioning process is obvious and requires us to try again. BTW, requesting a new server was the suggested solution.
Until you have the ability to resize the disks on a server, please do not default to something other than we requested.