I see🙂 You are currently still using the legacy workspace, which will eventually be migrated to the new workplace and use the new pricing plan which you can find here:
https://botpress.com/pricing
For now, 1 message refers to each message that your bot sends when speaking to the user. The 1k message limit applies to each workspace, so it will be shared between the bots ( so it's not 1k message limit for each bot)