Water over a charted depth and over a drying bottom

At 1316 the height of tide is 4.6 m. On the chart you find a charted depth of 5.0 m and, a little further on, a bottom that dries 0.5 m. How much water is there over each at 1316? And at low water at 1957, when the height will be 1.8 m?

Height of tide 1316

4.6 m

Charted depth

5.0 m

Drying height

0.5 m

Low water 1957

1.8 m