Assalamu'alaykum Wr Wb
What's the meaning of khamsa (Hindu-Arabic number 5) below jim waqf sign?
Appreciate your answer..thanks
As this sign is not a usuall sign that can be found in any Moshaf. I have a strong guess that it shows that this is the end of the verse in some of the verse counts as in the moshaf of Medina the verse ends there as ayat al-Kursi is of two verses there (See also How many ayaths are there in Al-Quran?). Else it doesn't make sense. See also page 37 in the Moshaf of Madina (Warsh) here.
To verify this we would need the source where you found this sign in, as therein it should be explained or we could deduce it from there.
Note that earlier scholars disliked adding to the qur'an copies (Moshafs) what isn't part of it, like waqf signs, verse number signs etc. as we have by know in all printed Moshaf copies, so these signs are not something important, even if in cases they are helpful nor are they agreed upon among scholars.