Plugged card in, before update Used was 7024Mb out of 15185Mb.
After update, 7123Mb used.
So perhaps they have upgraded the card sizes on the '17 refresh.
Should not be penalized if the cards they provided in the past are not big enough for map data now. Think they'd provide larger cards if buying maps or during a service. These things must cost pennies to make, you can buy 16Gb cards for £6...
The Toolbox has an option of MOVE TO EMPTY SD CARD under settings, maybe this will allow for a transfer to a new SD and for updates to fit? Its says provided by mazda...
Also might be able to get cloning tools to do it for you.
These maps are also not comprehensive updates as there were roads missing on the last update that had clearly been there for a year or so.