What does a post log provide details about?

A post log serves as a detailed record of what has already occurred in terms of broadcast events, specifically in the advertising context. It provides essential information such as air time, air date, spot rate (the cost of airing the advertisement), duration of the advertisement, and the ISCI code, which is a unique identifier for the ad. This information is crucial for advertisers and broadcasters to track the placements of advertisements, analyze their performance, and manage billing.

This contrasts with options that focus on forecasts or future planning, such as upcoming spot rates or available spots for scheduling, which do not reflect the retrospective nature of a post log. Ratings of a network, while important for overall performance, are not included in the specific details captured by a post log. Therefore, the correct option precisely identifies the comprehensive information that a post log provides regarding broadcast ads.