What does this expression of FIRSTNONBLANK function do?

[TungNguyen_19]

Hi everyone,

I received legacy Power BI report and in there I found this calculated column fomular:

USERGROUP =  IF(SystemLogs[Source] <> "Auto", FIRSTNONBLANK('ac Users'[TYPE GROUPS] , 0), "System") 

'SystemLogs' contains this calculated column and these tables have relationship:

In normal way I usually use is add other column which check Blank value for the function FIRSTNONBLANK but this function still work with scalar value? I have change the number to bigger than 2 and the result returns the same. What does this expression works? Can anyone else face to this use?

[Fowmy]

@TungNguyen_19 

Using FIRSTNONBLANK('ac Users'[TYPE GROUPS] , 0) in this case is same as MIN( 'ac Users'[TYPE GROUPS]  ). 
If an expression that returns a calucaltion is used in FIRSTNONBLANK in place of 0 then using it makes sense.