In the German version of Camtasia, when entering a duration for extend frame (or any property), using a comma will not work. Entering 5,4 will change to 54.
This behavior can occur if the German version of Camtasia is installed but the region on the computer is set to English. It also only happens when the decimal symbol has been manually changed. To resolve the problem open the Control Panel > Clock and Region > Region and make sure the Format is also set to German to match the installed Camtasia language.