Hardware sales breakdown for the last two weeks based on the Famitsu numbers found in this article:
Switch - 52,171/31,300
Vita production has ended in Japan, so that's why the console's sales don't follow a normal trajectory of decline after Golden Week. Its weekly sales depend first and foremost on people making up their minds to buy one while they still can.
You're subtracting Dengeki week 18 numbers from Famitsu's combined week 18+19 numbers.