The yellow package makes one gallon of STOCK solution. Best suggestion is to divide that among smaller bottles so you minimize the head space at the top of the bottols.
I suggest you DO NOT mix it down to 1+1 or 1+2 until you are ready to use it. And once mixed, it should be considered a one-shot developer (per printing session). Soup and dump (safely).
There are capacity charts around for Dektol based on 8x10 sheets. But in general, mixed 1+2, 500ml of solution fresh solution should be good for 20 to 40 sheets of 8x10. After 20 sheets, look closely at your highlights. If they suddenly stop "popping" or look grainy dump out and remix. Or, depending on the color tray you are using, if the solution goes dark and muddy it has oxidized and should be replaced.