Calculating Hyrdration

Howdy.  I am new to the whole baking bread thing and want to make sure I am calculating my hydration correctly.

• 300g  Bread Flour
• 150g  Whole Wheat F
• 296g  Water
• 15g   Salt
• 154g  Starter (100% hydation)
• 915g  Total Weight

My Math:  Starter divided by Two and add number to Water & Flour

Water (296+77) / Flour (300+150+77) = 72% Total Hydration

If this is wrong could someone help me understand my error? 

Thank you!