Negotiation room- Waiting For offer letter

I was selected in the walkin drive -TCS on 8 th feb for N/W security role, I got a selected mail also and uploaded my docs in ibegin TCS portal, waiting for an offer letter ,but i didn't get any HR contact !!

They just contacted me for a few verifications in the portal for all my previous company docs and verified (Green)!!

How long will it take from them to connect with me for the negotiation room ? Can I pitch more salary than what I said in HR initial screening(he asked the expected salary)