How is the travel allowance calculated on the first and last day if meals are provided?

On the first and last day of travel, the travel allowance is 75% of the total amount. The entire cost of any provided meals is deducted from this reduced amount. The remaining meal(s) are not further reduced. Reference Federal Travel Regulation ยง301-11.18.

Example: 
Breakfast ($18) and lunch ($20), totaling $38, are provided on the last day of travel, and the travel allowance reimbursement rate is $69; the calculated reimbursement amount would be:

Rate Amount x Factor - Adjustments = Calculated Amount

($69 x 75%) - $38 = $13.75