The Attack stat of the pokemon using Meditate will increase by 1 step (termed BTLs in the Gameboy description) on the Stat growth scale.
Because of the uniformity of the increases of the value, this increase translates into an increase equivalent to half of the original value of the Attack stat each time this move is used. In more definite terms, starting with no modifiers, the 1st use of the move will make the Attack stat 150% of the original value, the 2nd will make it 200% of the original value, the 3rd will make it 250% of the original value, etc.
Meditate will always fail if it has already been used 6 times by the same pokemon, without a move that lowers Attack being used on or against the pokemon using Meditate. This is due to the fact that a stat may only be raised by a maximum of 6 steps, until it is reset by the use of Haze or the pokemon is switched out normally. The maximum is the limit of how many increases can be applied to a stat. If another move increases the Attack stat of the pokemon using Meditate, the number of steps that it increases the Attack stat by will count toward the 6 step limit, and reduce the number of times that Meditate can be used appropriately.
An example of this last part might be the opposing pokemon using Swagger, which will cause an inrease to the Attack stat of 2 steps. If the pokemon with Meditate has not used the move yet, it will now only be able to do so 4 times before it will reach the limit.
