IFRS 15 – Contract Modification

Hi sir, please help me out with this one.

During the year ended 31/12/2018 coffee machine manufacturer receives an order
for 300 coffee machines from a retailer, at £500 per coffee machine (total order value
£150k), in 3 delivery batches.
01/08/2018 the first 100 coffee machines are delivered
01/09/2018 the retailer amends the original order by ordering additional 200 units.
The manufacturer agrees a 30% discount for the additional units (£350 per unit),
hoping to encourage further orders and a long-term business relationship with the
retailer.
By 31/12/2018 the manufacturer delivers 400 coffee machines (300 of the original
order, and another 100 towards the additional order).

Contract 1: Original units delivered
before the modification 100 x£500=50,000
Contract 2: Post modification units 105,000
Total revenue in y/e 31/12/2018
(200 original + 200 new – 100 delivered)
300 x £350 =155,000

Question:
1. The working for total revenue is not equal to 155,000, but equal to 105,000. Something wrong with the working? If the 300×350 refers to contract 2 (105,500), why £350 is used for the 200 of original contract? I’m confused with the calculation.

2. 400 was delivered. Why 300 is from original contract. In the original contract, promise 300, 100 was delivered. Isn’t the original contract should be 200, and the new contract is 200? I understand that the additional 200 + original contract of 200 is a separate contract from the 100 delivered contract.

It’s an a document in this article.
https://www.accaglobal.com/us/en/technical-activities/technical-resources-search/2018/october/IFRS15-revenue-recognition-steps.html