Travelling from Canada to Europe, how do I declare my movements within the EU at my initial port of entry? [closed]

I will be travelling to Berlin from Canada, connecting outbound in Brussels. After Berlin, I will fly back to Brussels for a few days before returning home.

When landing for the first time in Brussels (for my connection to Berlin) what does the immigration officer expect when they ask how long my stay is?

Is it:

• The entirety of my stay within the Schengen Area regardless of my travel within?
• Specific details of my itinerary, including my first connection to BER, my subsequent return to BRU and short stay before returning home?

I ask because the last time I visited (2015) I was in a similar situation with Germany, Denmark, and Amsterdam. The immigration officer at AMS seemed frustrated by the overly specific explanation I offered of my itinerary.

We also seemed to have different definitions of what "here" constituted when asked "how long will you be here" (EU/Schengen vs The Netherlands).