These companies have literally thousands of metrics - considering that they span multi-year time periods (as was the case here) - which could be tossed at them. There’s no way they can have all that in their heads at the time they testify. Congresspeople get to cherry-pick the ones that supposedly make their case and toss them out at the “witness” who will inevitably have a hard time responding, no matter who is on their staff.
The consequences of getting it wrong are absolutely zero. As indicated by this thread (and any number of comparable discussions of various blogs and such). Here she tossed out a number which seems to be blatantly contradicted by documented and verified information, and it does appear not make any dent to the adoring crowds, who just accept what she says on pure faith, and her status as “national treasure” to her ideological compadres is only enhanced. She - and others like her - have every incentive to make the most sensational charges in hearings such as this, with little regard for their accuracy.