I will do my best to offer guidance as I do not understand the language which is used in those screenshots.
Again as @Misbah mentioned and similar to my post above, you want to do a lookup which is SourceModule.SourceLineItem[LOOKUP: SYSTEMMODULE.First Month]
I was also not able to see the applied to column in your screenshot. Seeing that would help solidify my recommendation if you are able to take screenshots of the blueprint view which also includes the applies to columns that would be helpful.
Re: How to get only one value from a module that contains Time
In a time setting module what you could do is make this field calculated instead of manual selection.
You would have to create period start and period end line items (let’s call these Startoftime date and emdoftimeyear date) using the START and END functions against a Year time scale, date formatted. Then what you do is another line item which is Time Period formatted as Month and you have this Month time scale. Formula would be Period(StartofTimeDate), this should make this field calculated whenever you change System Time