回答
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The boss only gave me a rough explanation, so I'm having trouble understanding how to do the job.
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My boss's explanation of how to do the job wasn't very good, so I'm having a lot of difficulty.
雑 = rough, sloppy, not good, not well done
「rough explanation」というと「大体説明した」という感じがしますが、「poor」や「sloppy」というと、説明の中に間違いがあったとか、大切なことを言い忘れたとか。