I have noticed exactly the same error... $30 added to the Total Savings in the month of November, with that error still carrying through to the present day, now five months later. I noticed this when I went through my received items to make sure nothing was lost.
I was using the Total Savings to confirm that all items were received since there does not seem to be a way to display all the rewards links that were received. Yes, I can see the purchases and redemptions, but there is not a list of instant wins. I would be nice if there were a way to obtain the list of redemption links sent to my account. But absent that I was forced to use the Total Savings to verify nothing was missed.
Unfortunately, it seems even that number is inaccurate.