Here is the FIFA document on the proposed changes.
https://resources.fifa.com/image/upload/revision-o...
The formula for the SUM algorithm is as follows:
P = Pbefore + I * (W – We)
Pbefore: Points before the match
I: importance of match
I= 05 Friendly matches played outside of International Match Calendar windows
I= 10 Friendly matches played during International Match Calendar windows
I= 15 Group phase matches of Nations League competitions
I= 25 Play-off and final matches of Nations League competitions
I= 25 Qualification matches for Confederations final competitions and for FIFA World Cup final competitions
I= 35 Confederation final competition matches up until the QF stage
I= 40 Confederation final competition matches from the QF stage onwards; all FIFA Confederations Cup
matches
I= 50 FIFA World Cup final competition matches up until QF stage
I= 60 FIFA World Cup final competition matches from QF stage onwards
W: result of the match
1 = win; 0.5 = draw; 0 = defeat
We: expected result of the match
We = 1 / 10(-dr/600) + 1)
with dr=difference in ratings of the two playing teams, i.e. dr = [Pbefore of Team A – Pbefore of Team B]