True, he agrees to cut his wage from 300k weekly to the 80k weekly. I was surprised he did it just to join in Barcelona. He decreased his wage for almost 80%. That's crazy he did everything wear Barcelona's shirt. It gives me vibes he doesn't care to the MU.
Your figure is not correct. According to goal.com, it said Rashford took a 25% pay cut to facilitate the deal. He was earning £300k per week at Manchester United.
So 25% of 300k will be 75k.
To know the current salary, 300k - 75k = 225k.
It means he will be earning £225 per week at Barcelona.
https://www.goal.com/en-us/lists/bargain-purchase-price-pay-cut-terms-marcus-rashford-barcelona-loan-transfer-revealed/blt9bfbd0724ef31190