Negotiating an offer, is it too late?

I received an offer as a janitorial supervisor and I think the pay is a little low. It has been weighing on me all week. I have a competing interview next week. What wording worked?

Ask about the range, not a number on its own. It felt more collaborative.

I thanked them and said I was excited but hoped we could talk about the pay. They came back with a bit more.