without the when clause, the below example works ok

When I have

-spec get_NodeName(term(),term())-> R when R::term().
get_NodeName(FNodeType, NodeOrder) ->
	case {FNodeType, NodeOrder} of 
		{'PR', first} ->
				{"s",'F_PR'};
		{'GR', first} ->
				{"g",'F_GR'};
		{'PR', second} ->
				{"s",'S_PR'};
		{'GR', second} ->
				{"g",'S_GR'}
	end.

the indentation result is

-spec get_NodeName(term(),term())-> R when R::term().
get_NodeName(FNodeType, NodeOrder) ->
case {FNodeType, NodeOrder} of 
{'PR', first} ->
{"s",'F_PR'};
{'GR', first} ->
{"g",'F_GR'};
{'PR', second} ->
{"s",'S_PR'};
{'GR', second} ->
{"g",'S_GR'}
end.