overflow sound

I had a new toto carlyle toilet installed the other day and it flushes great.The problem i'm having is after you flush and the tank fills back up and then stops sometimes there is an overflow sound of water running down the drain, also when you use the toilet there is the same overflow sound, it only last a few seconds in both occasions, do I have any thing to worry about.

Thank You

Water stays in the bowl because the top of the trap is at the same level. Basically, as soon as you add anything to the bowl, it overflows to equalize the level. After you flush, the water from the filler goes down the overflow tube in the tank which fills the bowl to overflowing so anything added goes down the drain. What you've got is normal...