Process Instruction for Bulk Migration

I was asked below question:

I (actually our client) is using the bulk migration (apadm) to migrate workflow to a new version. They migrated one using Enterprise Manager and saved the instruction file. They indicated that the remaining workflow need to be in the same activity as the initial one. Is that true? Could you explain the NOTE in the User Guide - "match the original process instance exactly".

NOTE: Only process instances that match the original process instance exactly will be included in each batch migration, for example the target process instances have to be at the same running state as the original process instance. The bulk migration automatically suspends and resumes each of the process instances.

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Here is the situation:

After you created one process instruction and run the bulk migration with the apadm tool, the apadm tool will only migrate those process instances match exactly the same as specified in the process instruction.

You may group your process instances according to different running state, for example, you have 500 process instance currently in Manual Activity A (group 1), 200 process instances currently in Manual Activity B (group 2). You may create two process instructions, i.e. one for group 1 and one for group 2. Then run the process instructions with apadm tool.