Help with a recipe

Hey guys! 

So I was given a small amount of levain, along with a sourdough recipe for it, and the levain recipe (pictures attached).

I'm assuming it means the starter for this recipe, as the recipe doesn't have any starter (as you can see) 

I'm trying to break down the levain recipe so I could keep making more out of the amount I have now. 

Do you think the "levain recipe" is the "feed ratio" for this starter I was given? If so, is there a way to figure out what the "old levain" recipe is (that is on the levain recipe)?

 here are the recipes I was given with the levain and I would like to follow:

LEVAIN RECIPE:

White Bread Flour: 18#

Old Levain: 4.5#

Water: 10.5#

BREAD RECIPE:

92.6% White Flour

7.4% Wheat Flour

62.02%

14.82%

2.78%

Basically I'm trying to find out what the "old levain" recipe is (the one I was given an amount of) and if It's possible to treat it like a starter and keep using and feeding it.

When trying to translate the levain recipe to percentage (to find out how much I should feed my small amount with), I got to:

100% Flour

58.3% Water

25% Old Levain

does that sound right?

Thank you!!