TwoSix
Everyone's literal second-favorite poster
That seems to be to be using notes as a cognitive aid to the tracking of the shared fiction. You've already established in the fiction that the characters are in London, a real place that has a defined map. You could have improvised the situation, of course, and left it up to some sort of random resolution, but I imagine referencing a real place granted a sense of grounding within the setting.Here's an example from my own play of the use of notes (maybe that should be "notes"):
During a Wuthering Heights one-off, one of the PCs died. It had already been established that this took place in a bookshop in Soho, London. Another PC together with a NPC carried the dead PCs body in a box to the Thames, to dump it. It mattered how long this would take, because in the game a dead PC becomes a ghost within 2d10 minutes. To answer the question I Googled up a map of London. On the basis of this we decided that the body was dumped before the PC ghost emerged from it.
If you have the same situation, except the PCs are in Waterdeep, or Absalom, or Minas Tirith, and you pull out a map instead of resolving via random resolution, than I imagine it might invoke a similar sense of grounding within the setting.