Hi Alwina,
Great question! I had an offer from Google at L4 which is a mid-level position. 2 years is mid-level. 3+ years is potential for senior.
Other factors that are helpful is to share how much money you’re leaving on the table (A sign-on that you would have to return, a stock bonus that you won’t receive, a performance bonus that you’re missing out on.)
My last advice is to recognize that repeating the same argument to improve your offer has never worked. If your offer is 200k and you ask to improve it to 230k because you would owe a 30k sign-on, then they may offer 215k. If you mention again that you need it to be 230k because you owe 30k, be prepared to be rejected on your argument.