Was developing my last roll of Kodak 400TX last night when I realised that instead of measuring 300ml I poured 400ml into the beaker. Can't start all over again because I've just finished the small sample bottle of Rodinal that I have. It wouldn't be practical, a week before moving my things to Shanghai to open a new 500ml bottle of developer. So what do I do with 475ml of solution instead of the usual 375ml of 1+50 rodinal? I did a quick computation and found that 467ml of water and 8ml of Rodinal is equal to 1+58, so I figured if I had 16% more water than I should, then the concentration is 16% more dilute, so I developed it 16% longer in time compared to what I was planning to do at 1+50 concentration.
The resulting negative looks a little light, but still has quite a lot of details in it (maybe better even than 1+50 becuase of the diluted developer and longer time! but will have to scan it before I can tell). Overall, it was a disaster when I poured the solution into the tank, but it came out well! Phew!