How many bytes for a publish string

My data usage seems higher than expected. How many bytes are used to publish a string like this which publishes max temperature and a time stamp?

I think this would take 19 bytes for the text characters and 12 bytes for the numbers (assuming all integers are 4 bytes).

I had this saved from awhile back about data usage:

Thanks. that extra overhead for pings adds up to 230k/month.