Day 1: 75 shares x price = 13,179
price = 13,179 / 75 shares = 175.72 price per share
Day 3 : 75 shares x price = 13,293
price = 13,293 / 75 shares = 177.24 price per share
Return on Investment = (Final value - Initial value) / Initial value
ROI = (13,293 - 13,179) / 13,179 = 0.00865
0.00865 x 100% = 0.87%
If share is sold in Day 5 instead of Day 3.
Day 5 : 75 shares x price = 13,177.5
price = 13,177.50 / 75 shares = 175.70 per share
Return on Investment = (Final value - Initial value) / Initial value
ROI = (13,177.50 - 13,179) / 13,179 = -0.000113
-0.000113 x 100% = -0.011%
If I had sold my shares in Day 3, I would have gained positive ROI because price per share increased.
If I had sold my shares in Day 5, I would have lost a bit because price per share decreased resulting to a negative ROI