Advanced Shipping Price Rules - Shipping Cost on Category subtotal

 The ‘Cost on Category subtotal’ advanced shipping rules works with your flat rate shipping rules and settings. 

Using this, you can apply the shipping amount for a minimum and a maximum subtotal of items belonging to the added Product. And the amount or percentage entered in the ‘ Fee Amount’ field will be used for increasing, decreasing or using the same rate of shipping as per the category’s subtotal items in your cart. 
How it works:
Let’s say you have mentioned minimum category subtotal  ‘x’ and maximum category subtotal as ‘x+100’. So, it has created a range of 100 Category subtotal   
 
Now, to increase the amount for shipping for this range Category subtotal, keep the fee amount positive. To decrease the amount with increasing items, keep it negative.  
The fee amount will be added to the base flat rate shipping fee amount, which you’ve filled in the Fee section of the main form (Shipping Fee configuration) of this method. So, if you add $1, then the customers will be charged base fee + $1 for the x items while base fee + $5 for x+4 items.
Example 1:   Charge 50 to 100 item of a beanie with  Category subtotal with $10+ 
&& 
Charge 101 to 120 item of beanie with Pocket Category with $20+

Advanced Shipping Price Rules - Shipping Cost on Category subtotal

Advanced Shipping Price Rules - Cost on Product subtotal