I have 491 shares in Card Factory. When the sell price was 48.71p, the app showed the total value of my investment as £239.36. However, 491 x 48.71 = 23916.61, which is £239.16 or £239.17 depending on whether your round up or down. So, the total was about 19p or 20p too high.

I watched the sell price for a few minutes as it fluctuated up and down and I saw a variety of different totals each time it hit 48.71: £239.17, £239.22, £239.26, £239.31 and £239.36.

Can somebody explain how the value of an investment is calculated please? I’ve tried using the Buy price, the Sell price and an average of them both, but I can’t figure it out.

This appears to happen for all shares that are priced in pence. For example, I think I also observed a discrepancy of £7.62 for HSBC Holdings and maybe even £55.38 for Carnival this morning, although I may have mistyped the Sell price in my spreadsheet.