The discount applies for both the 13.5- and 15-inch variants of the laptop. These are the Surface Book 2 models that on sale:

13.5-inch with Core i5, 8GB RAM, 256GB SSD now $1299 | Regular $1499 13.5-inch with Core i7, 8GB RAM, 256GB SSD now $1699 | Regular $1999 13.5-inch with Core i7, 16GB RAM, 512GB SSD now $2199 | Regular $2499 13.5-inch with Core i7, 16GB RAM, 1TB SSD now $2699 | Regular $2999 15-inch with Core i7, 16GB RAM, 256GB SSD now $2199 | Regular $2499 15-inch with Core i7, 16GB RAM, 512GB SSD now $2899 | Regular $2599 15-inch with Core i7, 16GB RAM, 1TB SSD now $2999 | Regular $3299

While the models featuring a Core i5 processor are Intel’s 7th Generation, the models using a Core i7 processor are from the 8th Generation. Alongside the Surface Book 2 discounts, some of the Surface Pro tablets are also getting a discount. Currently you can get the Intel Core i5, 8GB of RAM, and 128GB or 256GB of storage $799 or $1099 respectively, which translate into $200 savings. This promotional offer doesn’t include details of when the discounts will end, as such you may want to act quick and save big on a Surface Book 2 and Surface Pro while the offers are still available.