What is going on in Acts 1:20?

In Acts 1:20 we read: > "For it is written in the Book of Psalms: > > > ‘Let his encampment become desolate, and may no one dwell in it.’ > > And: > > > ‘May another take his office.’" But Psalm 69:26 is actually uses plural: > "Make their camp desolate, with none to dwell in their tents." Psalm 109:8 has singular: > "May his days be few; may another take his office." (All translations can be found from the [USCCB website](https://bible.usccb.org/bible).) So it seems to me that St. Peter is changing the plural of Psalm 69:26 into singular in order to make a point. Then he quotes Psalm 109:8 in order to make a point. He seems to be just picking Psalm texts or changing the plural into singular in order to make a point. This is just confusing. I have been searching commentaries on this but have not been able to found one. This could be because people just take for granted that changing the plural into singular is a natural thing that people can just do. **What is going on in Acts 1:20?**