Hey, as long as you feel that you don't deserve it they will see through it. The fact that they are offering shows that the skills you have are enough.
The biggest leverage you have according to me is :
You can join right away. I would use it to negotiate. Emphasize the fact that you're willing to join right away if the right offer is right. Otherwise let them know that you would like to take a couple of weeks and evaluate other offers.(Make sure you give them a fixed date very specific, tell them that you're in process with a couple of other firms who are willing to offer 29L)
The biggest factor in your success or failure of negotiation would be your confidence. The more confident you are, the better your chances.
Hopefully, this helps and you get close to 29L. All the best!