Your logic is backwards. Stop and think. If you add the full amount of pensions (both the taxable and the untaxable parts) and the fully taxable amount of RMD payouts (which are always fully taxable) and report this sum on 4a and then on line 4b report the only the taxable part of pensions and the taxable amount of the RMDs then 4a MUST be greater than or equal to 4b. This is not higher math, just simple logic and arithmetic.
