In AV 'ability' is either material (Le 27:8; Ezr 2:69; Ac 11:29) or personal (Da 1:4; Mt 25:15) capacity. The mod. meaning ('mental power') is not found in AV.
He gave three thousand pounds to one, twelve hundred to another, and six hundred to a third, in proportion to the ability of each. Then he set out on his travels.
So the disciples, without exception, determined, in proportion to their means, to send something to help the Brethren living in Judea.