git-describe --contains

Please help me understand how this command works. There is one case in the linux kernel repository that puzzles me. Let's consider patch "drm/i915/ execlists: Reset RING registers upon resume" [1]. This patch was committed 641 commits after version 4.8-rc2:

~$ git describe bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae v4.8-rc2-641-gbafb2f7d4755

So I would expect to find it in version 4.8-rc3 and later versions.

However, if I search for the tag that follows (and hence contains) that commit, I do not find version 4.8-rc3, nor version 4.8, nor version 4.9, but 4.10-rc1:

~$ git describe --contains bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae v4.10-rc1~154^2~44^2~178

Why? Why not v4.8-rc3? This means that the patch has been included neither in v4.8 nor in v4.9, but only in version 4.10-rc1, right? Why so much time was needed, considering it was the 621st commit on top ov v4.8-rc2?

BTW, what are the numbers 154^2~44^2~178 that follow the tag name?

Thanks & Regards,
   Davide

[1] https://patchwork.freedesktop.org/patch/111587/