It's not a point of order; it's just a suggestion.
I don't know if this has ever been done in another committee before. However, by saying five to seven minutes, you're encouraging five but saying seven is okay. Perhaps at that five and half minutes you give a 90-second warning so that it's not an abrupt cut-off because sometimes it was like, “Times up; you're done. Sorry, no more.” With 90 seconds, people can then choose to wrap up.
By saying between five and seven minutes, we can politely say that five is requested but seven is allowed.