John Trumbull (June 6, 1756November 10, 1843) was an American artist during the period of the American Revolutionary War and was notable for his historical paintings. He has been called "The Painter of the Revolution". His "Declaration of Independence" (1817) was used on the reverse of the commemorative bicentennial two-dollar bill.
John Trumbull was producing artworks when he was 61 years old. 
This statement is correct because Trumbull's work, "Declaration of Independence", is dated 1817, meaning he did produce artwork during that year, which, according to his birthyear mentioned in the context, would make him 61 at that time. The system may have not been able to apply the math to resolve this. 
( z1 produce :ARG0 ( z2 person :name ( z3 name :op "John" :op "Trumbull" ) ) :ARG1 ( z4 artwork ) :time ( z5 age :ARG1 z2 :ARG2 ( z6 temporal-quantity :quant 61 :unit ( z7 year ) ) ) )