Not decrease increase it
In the second and the top line of hexagram 41 it says 弗損益之 "not decrease increase it". Fu, 弗, is a different 'not' than 無 or 无 (wu, without) or 不 (bu, not).
Fu is more like 'non-'. Non-decreasing, like the absence of decreasing. If you want something to grow in a healthy way, you should obviously not decrease it.
An exception is when things grew in a wrong way. Usually because 'something' increased or decreased them in the past. Then it is sometimes posible to mend the damage by reversing this.
On the other hand, when you try to help nature along a little bit, like helping a chick to come out of its egg or a butterfly out of its chrysalis, you will harm it.
So 'increase' is not right either. Non-decreasing is letting things happen by themselves. The way they do it naturally.
Non-decreasing gives nature the power to increase things. They can grow the way their inborn capacities demand them to. A tree can spread its branches, make strong roots, adapt to the spot where it happens to germinate. But when you water it daily, it will not send its roots deep enough to survive a dry hot summer on its own.
When you increase or decrease you carry out an act, you interfere with the nature of things.
Non-decreasing is being reverent. Giving things the freedom to grow the way they are meant to grow.