This page is intended to show the outline of the chip and to provide additional information that might not be clear from the data sheet.
Read the generic info about Xtiny and MEGAX.
The ATMEGA1680 comes in different casings. It has 16KB of flash and a maximum of 32 pins.
The ATMEGA1609 has more pins : 40 and 48
VQFN/TQFP 32