Firstly I should mention they are now saying the guidelines call for 13 to 15 years.
The plea bargain the judge rejected as too lenient was for 7 years, this is the same judge that will sentence him.
The feds have some kind of scoring system for whatever you were convicted of, the sentencing guidelines are based on whatever the score is. The judge can impose any sentence he wants up to the maximum, technically he could be sentenced for the whole 137 years or whatever it is. If the judge strays from the guidelines he has to file a reason why. This of course would be subject to appeal. If the guidelines call for a minimum of 13 years based on the previous actions of this judge I think it's safe to say he will get at least that.
FYI there is no federal parole, if he gets 13 he will spend 13 in jail.