Why only 10 project user defined attributes can be used in the condition in requisition approvals

Summary:

Why only 10 project user defined attributes can be referred in the conditions in requisition approvals when there are almost 20 attributes present which can be mapped to descriptive flexfields in the task 'Manage Project Descriptive Flexfields'. Is there any limitation in requisition approvals or any setup to be enabled to use all UDAs from Project ?

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23D

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