In Yeeflow approval form designer, you can summary the value of a sub-list field. For example, you can the summary you can save the summary value of a sub-list field to a separate variable. For example, adding up the values of a field, or calculating the average of a field, etc. The summary value will show at the bottom of each field like below:

Learn more about how to use the sub list control, please refer: Sub List (Approval form only).

The problem here is, the summary values will just simple show on the form, they are not actually saved to the backend database. Sometime, you might need to use the summary value on your forms or workflow. like based on the total value of the estimated amount to decide how to approve the request, or save the total value to a field when adding data to a data list etc.

For such cases, you can create a new variable on your approval form by adding a field control with the same type, or adding a new variable by click the variables button from the top-right of your form designer.

Then select the sub list control, find the summary field setting from the left properties settings panel, and click the "Settings" button:

Click the "Edit" button from the summary field (for this example, it's "Subtotal Amount"):

Then, on the pop-up window, find "Binding", and select the new added field control from the drop-down list.

Click "OK" to save your changes. This will save the summary value of this sub-list field (Subtotal Amount) to the variable of the field control (PT Total Amount).

You can then use the value of PO Total Amount for other calculations of logics settings.