They mean that if you take the maximum possible sentence that someone could get for each individual charge, and then added up all those individual maximums, you get their press release figure.
There are two big problems with that.
1. Various federal crimes are grouped for sentencing. Roughly, if one single act could be charged with N different crimes, and you are convicted for all N the sentence is not sum of the sentences for each, it is max of the sentences for each. An indictment, say, of 5 charges each with a 20 year max but that all fall in the same group would be listed as 100 years in the press release, but would really only be 20.
I find it appalling that the DoJ does not take into account grouping when writing press releases. Unlike point #2 below, grouping doesn't have much of a subjective component that won't be resolved until trial. DoJ has everything needed when they write the press release to figure out what charges group.
2. The maximum listed for each charge is what someone who committed the worst imaginable instance of that crime could get. Someone who had all the various factors that can affect sentence length go against them.
Unless you are doing your crime for a lot of money, as part of something like a drug cartel or the mob, people got physical hurt or there was a good chance they could have, you caused huge economic loses, and you have a serious prior criminal record, you ain't getting anywhere near the max.
First time offender, not for monetary gain, no one physically hurt, not doing it as part of some larger criminal enterprise? Somewhere near the low end, with a decent chance of just a few years parole instead of jail time.
Here are some articles. The first covers federal sentencing in general. The second two cover it in the context of the Swartz case and also look at each charge.
https://www.popehat.com/2013/02/05/crime-whale-sushi-sentenc...
http://www.volokh.com/2013/01/14/aaron-swartz-charges/
http://www.volokh.com/2013/01/16/the-criminal-charges-agains...
Short ver: DoJ: either make our prosecutorial life easy or we're going to harm you way beyond what is ethical.
Long ver: DoJ: You did A. Lobbyists have composed and purchased laws against A. Those lobbyists are pressuring their legislators to have us deploy high-profile Gov revenge on their behalf.
We want to charge you with B and have you accept that w/o resistance. To that end we are charging you with B,C,D,E,J,K,L,Q,R,S,T,V,Y and some Dr. Seuss letters we came across.
> On September 12, 2012, federal prosecutors filed a superseding indictment adding nine more felony counts, which increased Swartz's maximum criminal exposure to 50 years of imprisonment and $1 million in fines. During plea negotiations with Swartz's attorneys, the prosecutors offered to recommend a sentence of six months in a low-security prison, if Swartz would plead guilty to 13 federal crimes. Swartz and his lead attorney rejected that deal, opting instead for a trial in which prosecutors would have been forced to justify their pursuit of Swartz
Let's be clear, this isn't "here's a slap on the wrist and we'll let it slide", this is "we're throwing the book at you on trumped up charges", and require him to plead guilty to 9 felonies to avoid a potential 50 year sentence.
[0] https://en.wikipedia.org/wiki/Aaron_Swartz#United_States_v._...