Suppose a TV manufacturing unit wants to raise its inventories from 1000 units to 2000 units during the year. Expecting sale of 5000 units during the year, the firm produces 5000+1000= 6000 TV sets. Actual sale for the firm are 5000 TV sets during the year.

This is an example of:

Planned accumulation of inventories

Change in inventories may be planned or unplanned. In case of an unexpected fall in sales, the firm will have unsold stock of goods which it had not anticipated. Hence there will be unplanned accumulation of inventories. In the opposite case where there is unexpected rise in the sales there will be unplanned decumulation of inventories. Similarly, when the firm will have a rise in unsold stock which was planned, it will be called as planned accumulation of inventories. On the other hand if the firm wants to reduce the inventories, for which it purposely reduces the production of inventories, it will be called as planned decumulation of inventories. 

In the above case, there is "Planned accumulation of inventories". Following example will help you understand the above question in a better way:

Suppose the firm wants to raise the inventories from 100 shirts to 200 shirts during the year. Expecting sales of 1,000 shirts during the year (as before), the firm produces 1000 + 100 = 1,100 shirts. If the sales are actually 1,000 shirts, then the firm indeed ends up with a rise of inventories. The new stock of inventories is 200 shirts, which was indeed planned by the firm. This rise is an example of planned accumulation of inventories.

In the above question, the firm "Plans" to raise the inventories from 1000 units to 2000 units i.e. plans to accumulate the inventory and in the end manages to do the same. Therefore, we term it to be planned accumulation of inventories.