Normally when you pay the policy in full, then will get a discount. With monthly payments, cost more, plus they add fees for billing you monthly.
Now when you got the policy, then on the front page is a declarations which will show the (total) cost of the policy for 1 year. My guess with 2 payments of $180 each (x 12 months = $2,160) and you paying the balance of $700 is for (6 months) thus would be billed around May/June for the next 6 months.
All policies are written for 12 months, but depending how you pay, either annually (1 time), or semi annually (2 times per year) or quarterly, every 3 months or monthly.