Excel: Paying off hypothetical loan in 25yrs vs 30yrs? [on hold]

I am attempting to recreate an Excel Spreadsheet Dynamic Model (Figure 9.4) presented in my Data Warehousing Decision Support System course. I've uploaded a copy at the following link: Excel Link - On Google Drive

One issue I'm having is that the [Principle Amount] column in my Book's example does not show change ($0.XX) while mine does -- The book does not specify which way rounding is occurring, but does list that on a $100 prepayment every month the specified loan is paid off in Month 270 (mine shows 273 being when it is payed off, which I assume to be an issue with the change?)

One of the questions in my book goes like so: In the spreadsheet shown in Figure 9.4, what is the effect of a prepayment of$200per month? What prepayment would be necessary to pay off the loan in 25 years instead of 30?

On the first question (in my current spreadsheet for Figure 9.4) The effect of a prepayment being $200 per month changes the loan to have a [Total Payment] of $1,300.65 vs the original $1,200.65. This difference in total payment results in the loan (in my spreadsheet) being paid off in month 247 vs month 273.

On the second question What prepayment would be necessary to pay off the loan in 25 years instead of 30? I am totally lost. Can anyone help guide me here? I'm thoroughly confused as from what I am reading, the original loan with a prepayment of $100 is not even taking 30 years to pay off!? (272 months / 12 = 22.66666667 months...??!?)

I'm attaching a copy of what the figure in my book is showing for Figure 9.4:

Any assistance greatly appreciated. I feel like I am massively overlooking something but not seeing what it is.