Is the American green card number the same as the visa number?

Yes, it is very common to lose a 0, that is, the first 0, which will appear in passports and other places and become 8 digits. This is probably the custom of customs and immigration, and we don't need to know. But your green card number, you must add 0 and 9 digits, understand? When you are asked to fill in the green card number, 0 should be carried with you.