Taobao operators usually use marketing tools provided by Taobao, such as Taobao data analysis tools, data analysis software, etc., to calculate monthly bills. These tools can help Taobao operators track key indicators such as store and product sales, traffic sources, conversion rates, etc., so as to derive monthly bills.

Specifically, you need to pay attention to the following data:

1. Sales: This is one of the most basic indicators for measuring e-commerce operations. It represents the sum of all sales achieved within a certain period of time (usually one month). On Taobao, you can view the sales, exposure, conversion rate and other data of the current store by entering the "Sales Report" module in the "Taobao Data Analysis" tool.

2. Traffic: Traffic refers to the number of users visiting the store. On Taobao, you can view the traffic source, conversion rate and other data of the current store by entering the "Traffic Analysis" module in the "Taobao Data Analysis" tool.

3. Average order value: Average order value refers to the average purchase amount of each customer. On Taobao, you can view the current store's average order value, average order amount and other data by entering the "Sales Report" module in the "Taobao Data Analysis" tool.

4. Inventory: Inventory refers to the number of goods. On Taobao, you can view the current store's inventory status, sales trends and other data by entering the "Inventory Management" module in the "Taobao Data Analysis" tool.

5. Conversion rate: Conversion rate refers to the proportion of visitors who become actual buyers. On Taobao, you can view the conversion rate of various current marketing activities and their impact on sales by entering the "Marketing Campaign Analysis" module in the "Taobao Data Analysis" tool.

By paying attention to the indicators and changing trends of the above data, you can derive the monthly bill and make corresponding analysis and optimization adjustments