It says Isaac was born in Oud-Schoondijke probably is fairly close to the modern day Schoondijke just southeast of Groede. Oud-schoondijke used to be a little town but was destroyed in the '80 year War with Spain' in 1583. What happened was the the Dutch deliberately flooded the area in 1583 to prevent passage of the Spanish soldiers. It had some success but some towns and the countryside were destroyed.
It refers to an area out in the countryside so not a town. Its location fairly close to where Oud-Schoondijke used to be.