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1. Blitz has its own rating calculation method.
2. This rating is not identical to the General rating.
3. Combining the ratings involves adapting it to the General rating (the main idea is that the leader has 100 points, and all others have points depending on how far they are behind the leader).
4. Blitz does not contain the points of the General rating; they cannot be compared (!). These are just Arabic numerals that should be considered only as a criterion for the relative position of players on the rating scale. This is a dimensionless value.
5. We see the real rating numbers for each player for the first time only after adaptation, and the subtraction procedure (finding the delta) is inappropriate. It doesn't show anything. I will give an example again: we could consider the Blitz rating to be based on 1000 points, and then the leader would have 969 points at the moment, and the outsider would have 10.
After converting to a 100-point system, your example loses its meaning because we take away 869 points from the leader, but only 9 points from the outsider... :)
