Since my surgery, and perhaps with the residual tumour still growing in my brain, I've had difficulty remembering a six digit number long enough to get it from my cell phone screen into whatever web page or app I'm trying to use.  Since surgery, I've probably made mistakes in my MFA code around a dozen times and I've been eager to not lock any of my accounts because of this small deficit.  I easily adjusted by realizing I could remember three digits long enough to type them in, so by swapping back and forth I could learn the first three digits then enter them, then go back to the code to learn the second three digits then enter them, then gain access to my various accounts. I decided to train up on six digit codes by creating something that would generate codes for me so I could then enter them and keep track of how often I was correct.  If you know me, you probably already can guess I used Excel with a simple formula that looks something like "=rand()", or ...