For the last several releases Laserfiche has used a variation of the BM25 ranking function. There is a Wikipedia article on BM25 that appears to be accurate where you can learn more. Ranking documents by the number of times a search term appears would bias results in favor of longer documents. Probabilistic methods like BM25 attempt to remove such biases to assign more relevant documents a higher rank; this is why Laserfiche uses BM25.

Old versions of Laserfiche (before 8.0) do rank by the number of occurrences of the search terms. Users can still sort search results by the number of occurrences by the hit count column to sort by in the search results view in the Laserfiche client.