I am uncertain about the Codeforces rating system, as it appears confusing to me. In Codeforces round 890 -:
Friend 1, with a rating of 1126 and a global rank of 4550, experienced a rating increase of +71. On the other hand, friend 2, who held a rating of 1278 and attained a global rank of 4724, saw a larger rating boost of +82.
Friend 1 possesses a superior ranking and a lower overall rating compared to friend 2; however, it is puzzling how friend 2 managed to achieve a more substantial rating increase than friend 1.
if you don't know, for the first five contests, the extra rating is added, so may be it's friend 2's first five contests.
To make ratings converges faster, Codeforces give players initial rating of 1400. These points will be added as extra rating changes of first 5 contests instead of being added once, in order to make newcomers' rating looks increasing.
new accounts get extra rating for the first 6 contests.