Keyword in Search Terms - Repeat what's in title?

Hi,

When listing an item, in the Search Terms box, there is little info point that says “Help customers find your products using search terms that describe your product; separate words with spaces, don’t repeat what’s in the title, don’t use brand or competitor names, don’t use product SKUs or ASINs. Must be less than 250 bytes”.

Is it a golden rule for you not to repeat any keywords from your title in the Search Terms or do you interpret it as in not to repeat your whole title in the search term box? I understand you can drop in ranking if you do repeat anything from your title but wanted to have more clarifications about that.

Thanks in advance!