Yep, you need to give more info. The L:G (Liquor (water) to Grain ratio) determines the OG if you aren't sparging, the amount of water taken up in the expended malt is going to depend on the amount of malt (mostly)… It's all interrelated.
Wort volume is expressed as 'Cold Wort Volume" (~20oC) so if you want 4L to the fermenter you also need to have a target OG.
Work out exactly what you want to get at the end and you can get a very good estimate of what you need to put in at the start.
One free tip. Little pots on a stove will boil off a lot faster than you expect, we normally look for around a 10% reduction in the wort volume in a one hour boil, keep an eye on you could easily hit 50% if you cranked the stove up to full bore.
Mark