What is problematic with naming 2/3 "two out of three"? Give two reasons

Two out of three means that there are three of something, such as "I have ate 2 out of the three cookies, where what the fractions really would mean, "I have ate two thirds of the single cookie.

The name used for 2/3 can be two-thirds. Two out of three can be also used, but it can be problematic.

For example, when you say you got two out of three in a test, but the test was out of 50 marks.

Naming it two out of three is lengthy and can be misunderstood.