Sourdough

Thanks chef for your answer about my inquiry . If i plan to make a starter with flour that has High gluten ( 14 % ) , only this flour in the starter , so i have to mix 500g flour and 500g of water . But i don't understand what you have said to me that i  may need to add a little more water (about 1-3% based on the baker's percentage)  , so 500g of water i will mix with 500g of flour , is there any more water or what ?
and also i have a small inquiry ...