I thought the font size was set in the documentclass statement, like
I use lyx to create latex documents.
Maybe it is using commas instead of decimal points because you have it set to a European format somewhere.
Custom font size commands
The default LaTeX font size commands are rather limited. They do not allowed you to insert really large text. This is done for a reason, generally you wouldn’t need to. However if you feel you really need to have some larger text, you can define your own size command. The following example defines 50pt text with a 55pt line height: