The default GPS rate on the YachtBot Minis is 0.3Hz, 1 point every 3 seconds.
At this rate, a unit running for 12 hours would consume around 1.8 Mb of data. This works out to be around 0.15 Mb an hour.
For a 7 hour run, a YachtBot Mini would use about 1.1 Mb.
It is possible to run the YachtBot Mini at different rates which would either increase or decrease the total data usage, but for most cases 0.3 Hz is sufficient.