What is A number in item 1 of I-134?

[i134q]

Hi,

In Item# 1 of I-134 form they ask for 'A' number for permanant resident if I am not US citizen. What is this? I am on H1 Visa. Do I need to fill anything here?

Thanks,

[Murali]

Leave it blank if you are on H1b Visa.