disk partitioning question

[PorkPieCat]

guys i shrunk my os partition and then extended it again, and for some reason i lost 1mb during the process (i.e. i shrunk and extended a 200000mb partition and in the end was left with a 199999mb partition). it's not a big deal but i'd still like to know why it happened, and if i'm permanently losing a small amount of hdd space by this action?

thanks