Non qualified annuity withdrawal

I have annuity 3 years old I put after tax 100000 do to a situation I had to withdraw half 50000 after surrender fee and other fees 10% early withdrawal I net 420000 I got 1099r why am I paying tax on this money when I put in after tax 

Box 1 42000

Box 2a taxable is blank

Box 2b is checked tax not determined