The water should be 1/4 cup, which converts to 4 tablespoons
My one-cup measure is 250ml, so 50ml is one fifth of that. One fourth would be 62.5ml. 4 tablespoons plus half a teaspoon, aka a heaping 4 tablespoons of water.
You should definitely use digital kitchen scales to measure rather then doing guesswork. The worst thing would be taking too little or too much.
It would be a mistake to take too little, certainly, or much too much more. I don't see the likelihood of any problem with taking minor amounts more than PPH's ever-changing recommendations. 62.5ml of water as opposed to 50ml should not ruin anything.
My only objections to the advice to buy cheap digital scales is that they aren't very reliable/exact either.
Anyone here who was ever a teenager on a diet knows that where you place the bathroom scale and how you stand on it can make the difference between joy and despair. Same with kitchen scales.
We all need to do our best.