To Add Consumption Details GO TO- Settings - GO TO - In-house Inventory - click on products- click on create products:

Then update the services using this products. 

click on Add Service -

Select the Category of the service and enter the amount of usage of the product for that particular service and apply. 

And Create the inventory.

After the product is created, you can edit the consumption details, just click on edit the edit the product consumption details and update as on;