That spec is so inflated it's nearly meaningless. Real world measured performance might only be 10% of that, but it varies widely from one manufacturer to the next.
It's about as bad as a little paperback sized car stereo amp that says it's 1000 watts.
Now if you have 2 Sonys and one is rated 7000:1 and the other is rated 20000:1, then you can surmise that the 20000:1 model will have darker blacks and a more vibrant picture, especially with dark movies or dark shows. But comparing a 7000:1 Sony to a 20000:1 Samsung means absolutely nothing.
You don't specify what type of contrast ratio measurement those are.
The two most common that you will find are an on/off contrast ratio, and an ANSI contrast ratio. They are very different, and describe contrast performance in very different kinds of situations. They are both crucially important for a high quality image.