I am reconciling accounts for the first time after upgrading to Quicken Premier.

There should be no errors, of course... but I've seen over the years that the opening balance sometimes gets corrupted when Quicken changes its download connection method.  I've had to scroll back to the opening balance and reset it to zero... after confirming that the error in my reconciliation corresponds exactly to the bogus opening balance.   See if that might be the case here?

Is the difference between your Quicken reconciliation and the statement a recognizable number = some transactions that perhaps have the wrong date in Quicken and so is not included in the reconciliation?

If you go back to your last-reconciled date ("R"), does that balance match the paper statements from your prior version of Quicken?   If not, then some earlier transactions must have gotten modified or corrupted.  Recheck old statements until you find where things are correct.