.1 written is written as .10
.99 is closer to one
That makes .10 less than .99
For this reason, .99 is greater than .10
Another example you could grasp is .5 .17
.5 is written as .50
.50 is closer to one making it closer to 1 and thus .5 is greater than .17
Due to all of the explanations provided above, .99 is greater than .1