You need to provide more detail. Most likely this is a GS schedule position.

Most likely you can negotiate steps within the range but not a whole grade. E.g. you can negotiate to get bumped up from.a GS 10 step 2 offered to a step 4 but not to a GS 11 step 1. The reason is the position is usually set at a Grade, but not a specific step.

Its no skin off the hiring managers back to bump you up steps Human resource financing and budgeting is handled by positions not really by what step or by absolute cost. In other words having too many maxed out step 10s doesn't hurt the organization really.

Also you absolutely must negotiate for PTO now. You will never get another chance to do so. You should get credit for prior experience outside of govt. So if you have 5 years of general experience you should get 20 days per year. This also doesn't cost your hiring manager anything.

Less than 3 years of service - 13 workdays per year 3 but less than 15 years of service - 20 workdays per year 15 years of service and over - 26 workdays per year

HR is often at odds with the actual people hiring you. The people hiring you do not care about paying you more or giving you more pto, as long as it's justifiable. HR will try to lower your comp because that's their job. You have very strong negotiating power as if you have an offer they have already gone down a very long road to get there. If you walk they have to start all over.

Also if you need it, ask about relocation which is also often very generous in govt.