Sorry, but with this statement, you have clearly demonstrated that you don't know the principles of Elliott Wave Theory. This is called an Elliott Channel which is created when you copy the upper trendline to the lowest pivot points of the correction. This chart is not in log scale and should only demonstrate that the most likely downside of this move should remain within the channel. You can also call it an 80% channel if you want.

Your approach with the horizontal line is fine, but it completely ignores Elliot Wave principles and repetitive structure patterns. Also, your pattern with the horizontal line is a "descending right triangle" which breaks to the downside more often than to the upside.