I've done both - N/A & left it blank, both are fine. [C] [33] [] is what I've always used. These are trivial, you'l be fine either way and I don't blame you for asking.
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5th EAD
Sent to Phoenix Lockbox:
12/14/19
Received:
12/16/19
Biometrics/Approved:
TBD
Expiring:
05/14/20