block height 491,407 is true

you can see the first line in the readme file: https://github.com/BTCGPU/BTCGPU/blob/master/README.md
or you can see this height on the chainparams: https://github.com/BTCGPU/BTCGPU/blob/574a6e546dc5cf712f4299a05f2646a05dabc839/src/chainparams.cpp#L97

this is around October 25th. it is possible they miscalculated the time since it is impossible and finding blocks is sort of a luck base thing.