I've seen a few references to hydration and noted a good explanation at Shiao Ping's recipe entry.
"Bakers percentages are relative to flour weight (flour equals 100%) and every other ingredient is a percentage of this. Flour from the Starter is not counted"
That same entry refers to "White Starter @100% hydration".
When it comes to starter is this referring to the refreshment phase of mixing 1:1 flour:water to feed or is it making reference 1:1 to make a "sponge".