What determined a character's prestiege level post update?

I had some characters that were level 50 that ended up prestiege rank 2, on the last web to get to rank 3, and I had others in the same position ending at prestige 0. Was it overall BP spent on them or something else? I'm really confused as to how they did this math
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The number of perks you had + a bonus for every prestige level you already had.
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Prestige was based on current prestige + amount of perk levels you had.
Either a combination of both or if you were P3 you'd have gone to P9 (Max for compensation) or if you had all perks all levels you'd have gone to P9 (Max for compo).
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The full details was in the release information for the patch, https://forum.deadbydaylight.com/en/discussion/334951/release-information-6-1-0-mid-chapter#latest.
Edit: Changed link from PTB notes to live, and added information from the updated live notes instead of PTB.
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