Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Round | Name | Circuit | Date | Winning driver | Winning car |
| --- | --- | --- | --- | --- | --- |
| 1.0 | International Gold Cup | Oulton Park | April 9 | Tony Trimmer | Fittipaldi F8 |
| 2.0 | Caribbean Airways Trophy 1 | Brands Hatch | April 12 | Jim Crawford | Ensign N180 |
| 3.0 | Rivet Supply Trophy | Thruxton | May 31 | Jim Crawford | Ensign N180 |
| 4.0 | Donington Summer International | Donington Park | August 15 | Jim Crawford | Ensign N180 |
| 5.0 | Caribbean Airways Trophy 2 | Brands Hatch | August 30 | Joe Castellano | Ensign N180 |
Question:
How many rounds total were there on may 31?
Answer:
1.0