有关 a matter of weeks 的用法，《韦氏高阶》列出了五种用法，你的句子中的 a matter of 属于其中的第一种用法，指“小量”“少量”，英文解释是 used to refer to a small amount。例句如：

It cooks in a matter of (a few) minutes. [=it cooks in just a few minutes] 只需将它烹调几分钟。

They quarreled over a matter of a mere couple of dollars. 他们为了区区几美元争吵起来。

The crisis was resolved in a matter of a few hours. 危机在几小时内就化解了。

The ball was foul by a matter of inches. 这球仅仅出界几英寸。