Need negotiation tips

I got reached out for a role and during the first meet, I got asked my expected salary. I'm a grad and I said 12-14 lpa. The other person in the meeting smiled a bit and showed a bit of hesitation (I think) and said that I could always negotiate. So, high chance that he's trying to lowball me.

Now, the thing is, the startup's got like 7M in seed a funding and I also saw a college post saying that the company recruited a student from said college for a 26lpa package. Also it's a really small start-up.

I'm thinking of asking for 15+ now and would hence like some negotiation tips. Thanks.