Every MT4 account on every computer is counted in the limit. For example, with a plan including 5 MT4 accounts, two MT4 accounts may be set up on computer A and three on computer B, or any combination thereof.
MT4Professional can be added as long as there are licenses available. If the license limit has been reached, a popup will be displayed (see example below) where you may choose to delete a license from another account/computer. If you do not wish to delete a license click the “Upgrade Your Plan” link.