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Im assuming youre using object offset. It takes the ratio of scale between the object youre arraying and the object (most likely an empty) that youre using to offset it, and applies it to each next instance of the array. So if you scale the object by 2, and the empty has a scale of 1, it scales the each next instance by 1/2 compared to the previous one. Its the same effect as if you scaled the empty to 0,5 - each next instance would be half the size of the previous one. It also works similarly with rotation and position.
So if you want to scale the whole array, you have to scale it together with the empty.