Financial proof

Hi everyone! I’m looking to start my application soon and am confused by the wording of the financial proof.

If I apply on February 15th I need proof I have had the appropriate amount since Approx January 15th, correct?

Also for this proof does it need to be anything official? I’ve read it can just be a print off of a statement but not sure how they validate it’s accuracy then.

Anyone who has completed the application I would love your insight! Thanks :)