Garmins mapping is subscription based.
Did you get any free updates, perhaps all products but single update only so you could try them ?
Looks like a bundle with all Garmins mapping for Aera 660 is US$299 per year - https://fly.garmin.com/fly-garmin/support/pricing
You can buy single updates for individual products (bottom of price list) or annual updates for 1 or 2 products but this quickly adds up to more than the annual bundle price.
Ignore the Onepaks, these only make sense for multiple panel mounted devices.
If you had an iPad you could get all Garmin mapping products (with a Garmin Pilot subscription on up to 3 iPads) for AU$300 per year.
So cost wise an iPad my have been a better deal.
I believe the Aera is more readable in sunlight tho.