At startup the miner shows a notice that you must wait about a minute to get correct hashrate, but he ignored it, so he got some random number. I get 440H/s at stock clocks.
Could I please have your launch configuration + OS + driver version?
After 11.5 minutes:ZEC: 08/08/17-15:04:13 - SHARE FOUND - (GPU 0)
ZEC: Share accepted (140 ms)!
ZEC: 08/08/17-15:04:23 - New job from eu1-zcash.flypool.org:3333
ZEC - Total Speed: 260.951 H/s, Total Shares: 25, Rejected: 1, Time: 00:11
ZEC: GPU0 260.951 H/s
ZEC: 08/08/17-15:04:29 - New job from eu1-zcash.flypool.org:3333
ZEC - Total Speed: 261.559 H/s, Total Shares: 25, Rejected: 1, Time: 00:11
ZEC: GPU0 261.559 H/sZEC: 08/08/17-15:04:48 - SHARE FOUND - (GPU 0)
ZEC: Share accepted (156 ms)!