Sorry but it does make perfect sense and has for decades ... it is like balancing a checkbook. Now if the funds used for support was never paid from that bank account it would not match so review line 2 again. Part of line 1 includes all bank accounts which includes what may have been put in savings.
Line 1 is income + bank account balances at the beginning of the year income $500 + bank bal BOY $500 = $1000
Line 2 is amount from line 1 used for their support $100
Line 3 is amount from line 1 used for other purposes $200
Line 4 is amount from bank account balances at the end of the year $700
Line 5 says that lines 2-4 should equal line 1. 100+200+700=1000
