From your question it seems like you are attempting to calculate the total interest based on one cut-off amount whereas credit cards calculate the interest on a daily basis. They arrive at DPR (Daily Periodic Interest Rate) by either dividing your Annual Percentage Rate (APR) by 360 or 365.
So in your case it is
0.069% based on how your card company calculated it. This is used to find the interest on the previous unpaid balance. Remember, also, that there is a cutoff (usually mentioned by the company, for ex, midnight of a date at Eastern Time). So it may look like you paid on a given day (based on your transaction time in the time zone) but it reflects as payment on the following day if it is after the deadline specified.
For ex, if at the end of the first day of your 0% APR expiry your balance is $1000, then assuming 365, your interest for that day is going to be $0.69. If you maintain this same balance until the next billing cycle the interest you'll end up paying will be (assuming 30 days in that month), $20.7 (and odd cents).
If on the 10th day you spent another $1000 then your interest for the first 10 days is the same but your interest for the last 20 days each day will be $1.38 and your total interest will be $34.5
So on a day to day basis you accumulate interest which gets summed up on the day the statement is finalized. That is how they arrived at $25.XX
In the same excel sheet you could create another column that calculates the DPR and add it up. You may be off but that again depends on when the cutoff starts and ends.