Current NATO spending according to Wikipedia is a total of 1.036 trillion. You can see that here:
https://en.wikipedia.org/wiki/Member_states_of_NATO?wprov=sfti1#Military_expenditures
EDIT: Spending as of 2023 is 1.1 trillion:
https://www.nato.int/nato_static_fl2014/assets/pdf/2023/7/pdf/230707-def-exp-2023-en.pdf
This represents 2.5% of combined GDP, which is 49.8 trillion in total.
Resolution criteria are that NATO spending surpasses 2 trillion US Dollars for at least one year before the END of 2028.
If you have any information that might help inform peoples decisions, please post in the comments!
@EvanDaniel Nominal. Just makes it simpler, and I think either way the amount of time between now and then is nowhere near long enough for the nominal amount to significantly change without real change