Split mass addition process where the source is AP

Summary:

We are doing the split to mass addition where the source is AP.

Content (required):

We are doing the split to mass addition where source is AP. For example, we split to 3 unit. We also amend the cost.

1. What happened if the total of these 3 amount under the invoice amount?
2. Or the total of these 3 amount exceed the invoice amount?
3. How to prevent the above scenarios happened ?

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Code Snippet (add any code snippets that support your topic, if applicable):