At this stage you already have the salary offer, and the interviewer knows your prior compensation. You want to handle any salary negotiations carefully. You can get the offer increased, but if you push too hard, it often can come back to haunt you. A salary concession that is too large is the most likely issue your boss may hold against you in the future.
During the discussion you might want to say, “One of the reasons I left XYZ was that I felt I was making outstanding contributions, but I got the same percentage raise as several people who were just doing average
jobs. I want to work for a company where contributions are fairly rewarded. Are merit increases here really for merit, or does everybody get the same percentage?” This may make the boss think more carefully
about your future increases if you’re doing a really good job.