ELI5: Future stocks returns in the US expected below 2-3% accounting inflation

Could someone quickly clarify how this is calculated and whether this is jointly for the total US market as a whole or a predictor return for owning a US company? For example: if I hold VTI, then my expected 'possible' future returns for the next 10y could be less than <3% (source: vanguard) - what does that then mean for owning an individual stock like BRK.B? does this mean that BRK.B expected return could be < 3% per the same figures?

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source: https://advisors.vanguard.com/VGApp/iip/site/advisor/researchcommentary/article/IWE_InvComWhtRlRtnStkBndsNxTnYrs?cmpgn=SM:FAS:POST:070518:TW:XX:XX:XX:sf192612203&amp;sf192612203=1

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EDIT: added source for clarification.

Submitted December 24, 2018 at 07:52AM by crosmaxal http://bit.ly/2GErlXf