I think there is more towards these numbers 369 in the story than just the number plate and the date.
In one of the episodes when Shubhra was seeing the dreams about the numbers, they also showed something interesting about Sulekha.
She is sitting by the table, angrily thinking about something and at the same time she unknowingly starts scribbling on a piece of paper with a pen. When she gets to her senses in the end, they have shown that she has actually scribbled a symbol, which is made up of these 3 numbers. 3, 6 and 9.
Then she starts observing it carefully, and then the episode switches to something else.
It is only after this that she vanishes and goes to Jesalmer.
I think there's still some mystery around these 3 numbers that's yet to be revealed.