Rekordbox doubling slow songs' BPM when analysing

Because it thinks the song is 120, which is within that range.

yes but why would it think it's 120 when the beat per minute is 60?? Why not ignore it or leave it at 60? This is the problem.

Because the algorithm doesn't think it's 60 - because it was told to expect that the music is between 70 and 180, when it analyses the 60BPM track, it has features similar to a track of 120BPM and thus says "this is 120." It doesn't know how to ignore it or set it as 60, hence the range options.

Got it. So a case where you want to analyze your entire library like I usually would do in Serato ie. select all tracks and drag onto the analyze button and serato will analyze and auto assign the BPM to each track according to it's beatmatch, how do I do that in Rekordbox without having to select a range?

Both Serato and rekordbox have BPM range options for analysis, and both have the ability to selectively re-scan songs.

In rekordbox, if I come across a track which has been incorrectly scanned, I'll use a MyTag to flag it as "BPM - Half" or "BPM - Double" and then use the filter to select only those songs, and use the appropriate BPM range to re-analyse the songs.

What am saying is, with Serato, I can just simply click on none for range, and click analyze entire library and it will give each track the right BPM. How can I do this on rekordbox? I think this will resolve the issue for me.

Sorry, that's not an option within rekordbox.