When editing tag parameters, have in mind that what GN4 parses what you enters on each key press, and - if auto-justification is enabled - justifies text accordingly.

Thus, when you are about to enter, for example >h 12pt<, as soon as you type >h<, GN4 understand it as >h 0< and justifies text accordingly (your text seems to disappear from the WYSIWYG, if the WYSIWYG pane is displayed).

Then, you enter a space and 1, GN4 understand it as >h 1< (1 of default measure).

When you add the number 2, it's understood as >h 12<.

The fun starts when you add p, and the US notation is enabled in the system preferences (GlobalConfig - > EdAdmin4 > Applications Configuration > Client applications). Thus, GN4 understand it as "pica", and justifies the text as very large; this may take 1-2 seconds, causing a keyboard lockup, until you are allowed to finish what you were to type, e.g. add t of "pt", after which everything returns to normality.

See also

Tags editing permissions

Protecting tags against deleting