According to the federal government,

>We expect news businesses to receive from digital platforms a total compensation of $329.2 million per annum and spend about $20.8 million in transaction and compliance costs for negotiating their first deals under the Bill.

https://www.pbo-dpb.ca/en/publications/RP-2223-017-M--cost-estimate-bill-c-18-online-news-act--estimation-couts-lies-projet-loi-c-18-loi-nouvelles-ligne

All revenue in 2024 due to the bill will be counted. For example if Google pays some amount in 2024 to exempt themselves in 2025, it will be counted as 2024 amount.