Incorrect:
As the temperature increases the N1 will increase to the Flat rated temp (around 30C) then the N1 will start decreasing again until you get your Assumed Temperature N1.
The ATM reduces the N1%, not increase it.
ATM is a method of reducing engine N1% when a suitable performance margin exists.
ATM and FMC N1% prior rely on the correct temperature input in FMC PERF INIT.
The baseline figure used by FMC is the N1% based on OAT, reducing the temperature reduces this N1%, a lot in this case (+16C to -52C).
You then reduce N1% further by enabling the performance reduction using ATM, in this case -52C to +50C, a huge reduction of N1% on top!