Sourdough 50/50 WW/white flour bread with butter and pumpkin seeds

So after the low yeast version I baked a while ago, I baked some more of those. 

Then I wanted to use my own sourdough culture to bake that bread. 
I had some trouble getting the hydration right, because I feel like the use of baker's percentage is a bit harder when using a sourdough (another source of flour and water) to aim for a certain hydration. 

I used 

300 grams whole wheat flour (50%)

300 grams white flour (50%) \

                                               100 grams sourdough, 58 gram flour, 42 gram water

420 grams water (70%)            /

12 grams of salt (2%)

30 grams of butter (5%)

and a handful of pumpkin seeds.

I mixed all of the WW flour, all the sourdough and 258 grams of water the night before. 

In the morning I mixed in 242 grams of flour and 120 grams of water, the salt and the melted butter.

Kneaded with handmixer, left to rise an hour. Then shaped into a boule and put seam-side up in a banneton. After 2 hours proofing turned on a peel and scored and baked in a steamed oven on a stone for 55 minutes at 190 C.