Be aware that the indicated offer is only the estimation and it's impossible to predict exactly the Minecraft consummation and attitude. It will depend of the server configuration, plugins, mods etc. identical servers with plugins and mods could be completely different in terms of real resource consumption.
For example, a Pixelmon mod will consume much more than a simple decorative mod. Furthermore, there are various optimization options in the form of plugins, mods, or configurations that can impact server performance and thus alter the actual consumption, potentially skewing the estimation provided by this guide.