The ratio of tiles to lights is 108 to 9, which we can write as 108:9
This ratio has any number of equivalent ratios which you find by multiplying or dividing both numbers by the same multiplier. You could double this to find the equivalent ratio of 216:18. You could divide both by 9 to find the equivalent ratio of 12:1 - this one is called a unit ratio because it the number of tiles per 1 light.
