If your bottle is 1L.
So you have 700mL of acetic & 300mL of water (70% acetic solution)
If you add 1L of water you'll have
1300mL of water & 700ml of acetic so a solution of 35% of acid acetic
it can be a start point for calculating
when raised enough the volume of water to get your 5%, just took 150mL of that solution