The suggestion above to weigh it is what I have done when making a similar mistake. 100mL of water weighs 100g. 100mL of fixer concentrate weighs 134g. For 1+4 you're looking for 100mL weighing about 106.8g. If it's not the right concentration it's unlikely to make much difference anyway.

Edit: I've just read the posts properly and if there's sediment it means that the fixer is partially decomposed. Maybe it's ok for film (you can tell by looking at the results) but I'd not use it for paper.