You sure that's working as an exact match? I've noticed most punctuation characters are ignored (with the possible exception of the apostrophe, it appears).
I await the reply from the lexicographer who takes issue with my implication that parentheses are truly punctuation marks
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If you're getting impressions, they may be broad.
You could do a test.
Enter a wild phrase like (green zebras) and search for it. Then assuming the phrase is worthy of broadmatching, try some variations and see where they go. Be sure not to have broad or phrase matches of green zebras that could compete for the impression.
FWIW, I've had clicks and impressions on truly implausible [exact match] typos that I've made. I wonder how the errant paste job which resulted in "[red widget]" managed to get a lot of impressions and clicks.
Also, who knows, green zebras could end up converting really well :)
patient2all