set⁵

The set of four records, $\$frac{\text{offered}}{\text{A}} for a limited time only, $\$frac{\text{are}}{\text{B}} available $\$frac{\text{exclusively}}{\text{D}} in the stores mentioned. (TOEFL)

the set of four records 表达的是复数概念,为什么它的谓语动词要求用单数?