How random is random in kode

I had been using a flow with a file picker to randomly select an image from a folder to use as background in klwp everytime my phone is unlocked.
I then ditched it, and used the function mu(rnd, 1, 140) to generate a formula to retrieve the same files, cautiously named ( wall-n where n a number from 1 to 140).
In both scenarios, it somehow feels like the random numbers returned are not that much random - I keep seeing the same files over a period of a week or so.

Any thoughts?

Of course I might just go wild and use another way to produce random numbers - getting the current time and manipulating the numbers comes to mind but before going into that I thought of getting thoughts from others first.