The variables to make it are already there. Lose $320, Win $2,320 = $2000 Profit.
Need to know our "average range target".
If it was 5 points for example I think we'd require 464 shares with a 0.17 stop.
The winner in your example is 7.25 times the size of the loser which is probably low odds.
You have it wrong and the Expert hasn't corrected you.
There are 4 losers in his hypothesis. You have lumped them together as one to get a ratio of 1:7.25. The actual ratio is 1:29. Each trade is an entity on its own and in this hypothetical scenario would involve 5 X $80 risks, 4 of which are losers.
If you use 1600 shares you can afford a 5c stop loss but need the winner to yield $1.45.
If you go down to 800 shares you can afford a 10c loss but need $2.90 winner.
At 400 shares its 20c stop loss but needs $5.80 winner.
With an 80% loss rate the hypothesis can only be for probing a range looking for a break-out. Bear in mind that 3 losers causes stress and the exponential increase with each thereafter can cause damage.
Unless you are prepared to sit palms together pointing skywards for hours or days on end think again.
Use 10 trades in the W\L & R\R matrix. put the numbers in the W\L columns eg. 2:8, 3:7, 4:6 etc. Look at the instrument\s of interest and determine recent daily range.
Nobody ever gets a quart from a pint pot so be realistic. If you cannot reasonably expect to get an entry with a minuscule stop without getting hit 80% of the time it's a no go. and if an unusual move is required to provide winners of the size to make a profit it again is a no go, absolutely.
Once you get the idea of working win loss and risk reward ratios together and apply them to instruments of interest you approach the hard part of trading and may conclude that the best part of the equation to work on is skill level in selection and placement which by skewing the W\L ratio in your favour is not only more satisfying but increases chances of ultimate success.
Running a scatter-gun approach over multiple concurrent trades is comparable with investors who buy many different shares in penny stocks knowing that most are likely to fail but some may rocket into the stratosphere and cover all the losses with profit. For a trader, time is a luxury in thin supply.