10b is only if you take the Standard Deduction. Are you sure you aren't getting the Standard Deduction on line 12? How much is on 12?
For 2020 the standard deduction amounts are:
Single 12,400 + 1,650 for 65 and over or blind (14,050)
HOH 18,650 + 1,650 for 65 and over or blind
Joint 24,800 + 1,300 for each 65 and over or blind
Married filing Separate 12,400 + 1,300 for 65 and over or blind
