Why * 1.00? Around 5 mins in.

1.0 or 1.00 or 1.000, is the same thing.
She is using a decimal to force implicit cast to decimal from integer division.

This is because count() returns an integer value. One way to make it non-integer is to multiply by 1.0.
I hope I've answered your question.

to convert , let say 12 into 12.0 , she multiplied that by 1.0 , now the success ratio, which should be in percentage(which can be in decimal) to bring that. she did so

Thank you both for your answers!