Is there a good detailed reference for stock trading volume?

 

I've been reading about stock volume but everything I've seen talks about it at a fairly high level.

I read that we use Lots and that a lot represents 100 shares. If we specify a lot at 0.5 it means 50% of, or 50 shares in this case...and that's called an Odd lot size.

I was doing a trade with my demo account and it wouldn't trade using a 0.1 lot size. I kept increasing it until it finally worked, which was 1.0. I don't understand why that was the case?

This is my understanding of what Lots are for stocks. I read it's different for currency trading but I'm not doing that.

Have I missed anything regarding my understanding of Lot volume for stock trading?

Thank you...

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