In its March 11, 2019 announcement of OpenAI LP, OpenAI said returns for its first round of investors were capped at 100 times their investment, that it expected the multiple to be lower for future rounds, and that any returns beyond the cap would be owned by the original OpenAI Nonprofit. The cap was the defining feature of the “capped-profit” label.
Note on sourcing: OpenAI’s pages return HTTP 403 to automated fetchers; the 100x figure was corroborated through search against the canonical openai.com/index/openai-lp/ post.