Change suggested clock speed from 1 MHz to 10 MHz.
To use 1 MHz speed, one needs to re-burn the bootloader.
Trying to use 1 MHz speed without re-burning the bootloader
results in a clock that is slightly fast (delay(1000)
will actually act more like delay(800))

See note in SpenceKonde's githup under 'List of Tools
sub-menus', under Tools -> Clock Speed