Once removed means there is a 1 generation difference between you and your match. Sometimes knowing the ages of the compared individuals can be helpful, but it does not always work that way. For instance, if you have a 1c1r a first cousin once removed, you can take the older person and go up 2 to their grandfather, (the younger persons great grandfather) go back down two to their first cousin on their same generation (the younger persons parent) and then go down once more for the once removed to get to the match.