Pressing a 0-9 digit accumulates that digit into what is named
the "modifier". That modifier affects the behavior of many
keystokes described below. The modifier starts at zero, but
most commands interpret a zero as a 1 so that they can have an
effect.

'G' selects the block specified by the modifier as the current
block. Any change madde to the previously selected block is
saved beforehand.

'[' and ']' advance the selected block by modifier.

'Return' resets the modifier