The limited number of messages

Hello everyone,
I would like to ask about the number of messages I can send through cayenne.
I know I’m limited to 300 messages but is this number per month??. so every month I can send only 300 messages. Or if I reached this number I can’t send anymore messages even after one month.??

it is limited for 300 messages per day. if you crossed this limit, your device won’t be able to send any more message.

Thank you for your fast response .