If I ask a girl for her phone number before she earns my interest, isn't it demonstration low value? Because my behavior(asking her phone number) definitely shows my interest in her, but she has not yet earned my interest.
However, if I don't ask her number, I will never see her again. Please advise.

Charm them enough and they will ask for your number.

Or just give them your number if you will.

But to be honest. It doesn't matter. It's over thinking.

If 2 people are attracted to each other , doesn't really matter about all this DHV / DLV bollocks.

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USER HAS BEEN BANNED FOR REPEATEDLY IGNORING MOD WARNINGS AND MULTIPLE RULE VIOLATIONS

I think it depends.
It can be a DLV as much as an IOI or a hoop

I never ask for a girl's number. I TAKE the girl's number. I don't give her the option of saying no.

I converse with her, and at some point later in the conversation, I hand her my phone with the contact page, and tell her to put her information in my phone so that we can meet up again. When she is doing this, I just continue the conversation as if nothing happened. Getting a phone number is not a big deal, it means nothing, it is only a means of continuing the interaction later.

A number is not a big deal, it is just a number. Occasionally you will have a girl give you a fake number, and you will occasionally have a girl flake later... this just reinforces the point to me that numbers are not a big deal. You aren't asking her to marry you. Girl's don't take a number exchange seriously and neither should you. Just TAKE it, and don't make a big deal out of it.