AutoComplete rule Object Validation Rule Type for Promotion is giving error while hiring

Summary:

i have created simple code for promotion validation and the code is working fine when promoting but giving error while hiring an

Content (required):

the code is built to compare 2 numeric dff at grade level while promotion and raise error

Version (include the version you are using, if applicable):

22D

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