Reducing the credit period by 29 days will increase cash by 29 x 4.383 = 127,136, which I think has been rounded, rather confusingly, to 125,000.
Payables are incurred at 1375/365 = 3.767 days are currently about 20 and if this were increased by 20 to the more normal 40, then (40 – 20) x 3.767 = 75 extra would be kept in the bank.