The Reorder and Minimum order quantity is defined based on  fixed consumption pattern.
When you select the Stock Group under the Reorder Levels menu, the Simple Reorder  Levels screen will be available, by default.
Go to Gateway of Tally > Inventory Info.  > Reorder Levels
Select a group of Stock Items from the List  of Groups, to specify Reorder Levels for the Stock Items in the Specify Reorder Levels screen. For each item in stock, you can  define a Reorder Level and the Minimum Order Quantity.
The Simple Reorder Levels screen  appears as follows:

Reorder Quantity
Enter the level/quantity in the Reorder quantity  field.
Minimum Order quantity
Specify the minimum order quantity required based on  economical order lot predetermined.
In Simple Reorder Levels screen, the  consumption alternatives will not be available and hence you have to input the  only the quantities. i.e., the options that you have in the above mode are to  define Reorder Quantity and Minimum Order Quantity.
If you have used Advanced Reorder options earlier, click  Simple Reorder button, to specify simple reorder  levels.
The options available in the Reorder  Levels screen are as follows :
R : Adv Reorder
Press Alt+R to toggle to Advanced Reorder Levels screen.
M : Adv Min Qty
Press Alt+M to toggle to Advanced Minimum Order Quantity screen