I'm not sure exactly how they count it, and my husband was paid weekly at his first (of two) job in our Category B application. I counted back 12 months from our application date, then included two more weekly payslips on top of that, and I had 13 full months of bank statements that showed every payslip going in. One extra payslip and bank statement won't confuse them, and it reduces anxiety for you.
As for what's in the bank statement, don't worry about anything other than them being able to find the deposits that correspond to the payslips. They literally don't care about anything other than verifying you were paid what the payslips say you were paid.