Easier to visualize if you just plot it.

Start with total mass is 100 kg, and 99 kg water, and 1 kg dry. Let x be the kg of water removed. Then the ratio of water to total mass is

(99 - x)/(100 - x) Plot: https://imgur.com/a/oDaKLVo

It's intuitive that until x becomes pretty large, there is negligible effect on the ratio.