In the README the relevance in TrecQrel format is described as "how relevant is docno for qid" and the example below has values 0, 1 and 2 for it. I'd have three question on this:

1. Is 0 the most relevant docno and 2 the least relevant or vice versa?
2. Can I put any non-negative integer as the relevance?
3. Are float numbers supported?

For context, for each query I have a list of documents and a number how many times each document was opened by a user (hits) after the query. Now I'm not sure if I can use the hits directly as the relevance number, or if I should scale it or just order documents based on it and then use the index.