Only the order which was placed on a Friday and T+2 being a national holiday has an exception for dispatch on the next day. To explain it further, If an order was placed on a Friday, then T (date of order placing) +2 days = Sunday. Here, we do not charge a penalty if the order was dispatched on Monday i.e (T+3).
And hence, here Day of Dispatch = Day 2 = 23rd Apr | Day of Delivery = Day 4 = 25th Apr
However, if the order was placed on any other day of the week than Friday then, the standard time for SLA is T+2. If the order is dispatched on the 3rd Day then it is still considered an SLA breach.