Updates since the previous commit point Vs updates prior to the commit point The quote below is from An Introduction to Database Systems, 8th edition, C J Date. 

I am confused since I think "all updates since the previous commit point" is the same as "updates Prior to the commit point". Am I wrong? 


  ...all database updates made by the executing program since the previous commit point are committed; that is, they are made permanent, in the sense that they are guaranteed to be recorded in the database. Prior to the commit point , all such updates must be regarded as tentative only-tentative...
The text must be talking of two different commits during the same database session.

Say, the last commit that happened in this session was at time A. Now if you make a second commit at B, all updates made since A (the previous commit) are committed. Prior to the commit at B, all such updates are only tentative.