The headlines describing this as 'Beyond TOP SECRET' are not quite right -- Special Access Programs are technically "TOP SECRET" programs, but there are then further restrictions on access. That's actually not unusual for military programs: we already knew she had TS/SCI data in her emails, and SCI represents a TOP SECRET level of information that is further compartmentalized. In fact, the disagreements about whether SCIs are SAPs is sufficient that I'm not clear on whether this is even new information: the IG report may simply be acknowledging the two TS/SCI emails we already knew about, although FOX News says that is not the case.
In any case, it's big money. If it's additional to the two emails we already knew about, it's huge. If it's a confirmation that the IG considers those two emails to be TS/SAP, it's still really big because it confirms she violated security with incredible recklessness. Violated it for, let us remember, mere personal convenience and to shield herself from being subject to the ordinary public scrutiny that American officials lawfully owe to American citizens.