I seem to remember those values quoted are correct.
The clicker adjuster (I have one too) is designed for agricultural machinery with tappet adjusters with a slot in the top. Hence mine has not seen any use on a Lancia as Lancia Fulvia engines use a 3mm? square top.... so you need a little slot spanner (and feeler gauge)
The clicker type of adjuster is great in as much as it takes out wear in the top of the valve stem where it is being hit by the tappet. This may be an issue (was for me on one engine) if the engine has been rebuilt with valves without hardened (stellite) tips. A feeler gauge goes stright across the dent in the top of the valve giving a false reading/ very tappety engine.
I have a lovely gadget that sets tappet clearances based on the required clearance and the thread pitch of the adjustment screw.
The principle is very simple, a 'clicker' system gives an audio output to the angle through which the adjustment screw is turned, which can be translated into a gap measurement based on the thread pitch.
This far too difficult to describe in words ..... here is a link to a currently available version!!
https://www.frost.co.uk/gunson-clikadjust-tappet-adjuster.htmlI hope I can find mine as it is so simple ...... Recently I have been using a spanner and feeler gauges, but the tool is far quicker and easier.
Andy