Update instructions.md

Co-authored-by: Anastasios Chatzialexiou <[email protected]>

Author: ErikSchierboom

exercises/swift-scheduling/instructions.md

@@ -35,6 +35,6 @@ There are two variable delivery date description patterns:
 | Description | Delivery date                                                          |
 | ----------- | ---------------------------------------------------------------------- |
 | `"<N>M"`    | At 8:00 on the _first_ workday<sup>1</sup> of this year's N-th month  |
-| `"Q<N>"`    | At 8:00 on the _last_ work day<sup>1</sup> of this year's N-th quarter |
+| `"Q<N>"`    | At 8:00 on the _last_ workday<sup>1</sup> of this year's N-th quarter |
 
 <sup>1</sup> A workday is a Monday, Tuesday, Wednesday, Thursday, or Friday.