table-time-before-update

table-time-before-update is a variable defined in `table.el'.
Its value is

0.2

Documentation:
Time in seconds before updating the cell contents after typing.
Updating the cell contents on the screen takes place only after this
specified amount of time has passed after the last modification to the
cell contents. When the contents of a table cell changes repetitively
and frequently the updating the cell contents on the screen is
deferred until at least this specified amount of quiet time passes. A
smaller number wastes more computation resource by unnecessarily
frequent screen update. A large number presents noticeable and
annoying delay before the typed result start appearing on the screen.

You can customize this variable.