This entry was made entirely in RCT1. The only available scenario that has the proper size is the Micro Park scenario, which is a 15x15 park. OpenRCT2 automatically converts the .sv4 file to its .sv6 format, although some things may be lost in translation if you don't have RCT1 yourself. I made an imgur album of how it looks in RCT1: https://imgur.com/a/UYnFfsr