Retirement tax questions

Last year's 1040 shows the Total IRAs, pensions and annuities in Box 4a as $45,516 AND a Taxable amount in Box 4b of the1040 as $45,192.  The amounts in those two boxes are different, so it appears to me that the answer to the question "if you computed part of your distribution in past years as being nontaxable" is yes, because the 1040 implies that $324 of the total is non-taxable.

The fact that the1040 indicates a non-taxable portion also indicates the Simplified Method was used last year, correct?  And if it was, that worksheet isn't included in the paperwork from H&R Block.  :(