In an engineering context, I would interpret it to be "roughly ten times", because that is what it means. And the same argument,that if they meant something else, would just say "three", or what have you.
In this case h-d is 8x, d-w is 5x, w-m is 4x and m-y is 12x.
This is after all just unimportant pedantic, but if clear and simple communication is the goal, it probably makes more sense to describe it as the next calendar unit up.
That is beyond the point, since the OP changed the magnitude with every size. If it was 8x at each iteration, we would've had less pedantic comments here
In this case h-d is 8x, d-w is 5x, w-m is 4x and m-y is 12x.
This is after all just unimportant pedantic, but if clear and simple communication is the goal, it probably makes more sense to describe it as the next calendar unit up.