I think the English translation: "You may decide", although technically correct, is somewhat ambiguous, since it could mean: You may decide, or you might not expressing doubt as to whether you will make a decision. The German sentence "Sie duerfen entscheiden" on the other hand, clearly means: "You are permitted to decide" and does not stray into the territory of whether you will or will not decide. I don't know how to translate that back into German, but you would start with: "Perhaps you will decide" and go from there.
Hi guyhoschke, as you may know, the aux. verb 'dürfen' is conjugated in present tense as follows: ich darf, du darfst, er/sie/es/man darf, wir dürfen, ihr dürfst, sie/Sie dürfen. From this one can see that 'Sie dürfen' as used in DL's sample sentence cannot mean 'she may'. 'Sie' (+ 3rd person plural 'dürfen') can here only mean 'they may' or (with Sie capitalized) 'you may'.
Hey Chidubem15! If it were to have been "She may decide" then it would have been "Sie darf entscheiden.", but because it's "Sie dürfen entscheiden" we can interpret that it's either saying "They may decide," and/or "You (formal) may decide,". Hope this helps! Feel free to ask any more questions!