Is "in", "out" an abbreviation form of something?
In this particular context, no. It is not an abbreviation for something. When she says the line, "I'm in first. I'm out last," she is saying that she is the first person to arrive at work and the last person to leave work. Usually, "in," "out" refers to entering or arriving at a specific location and leaving a specific location. Most of the time, the speaker won't say the specific location, it is implied in the conversation or is usually said by the other person. Here are some examples: A: Should I come into the store with you? B: Nah. I'll be in and out. Ex: She got in to work last and was out first.