Spoiler ahead: although in fairness, you should all have seen Dr. No by now or else shame on you for missing this film classic.
When Professor Dent shoots "Bond," he doesn't scatter the shots in any way. There's no reason for him to believe it's Bond over Miss Taro. Before they were both in bed. Since he didn't see her on his way into the bedroom, or hear her moving around in the kitchen or bathroom, there's every reason to believe she'd be in bed with Bond or Bond could be in the bathroom leaving her in bed alone. He doesn't scatter his shots in any way, so he really could only have hit one of them, if they were both in bed and Bond is sitting basically in the dark, so it would be hard to tell whether there was one body in the bed or two.
I'm just saying, Professor Dent is taking an awful risk, although I suppose Dr. No wouldn't care if he loses just one more minion.