PM Technical articles

Hi, I am currently reading technical article from ACCA website title All about budgeting-part 2. For the rolling budget example given in this article, I am having a problem to calculate the direct labour and direct material. According to the suggested answer, direct labour and direct material are vc and increasing by 3% every quarter. But why the direct material for Q4 (X8) and Q1(X9) are 26750 and 27552? Aren’t they supposed to be 31900 and 32857?