The system will be listing the investment fund which is tradable in its own right and what it has invested in
The list of companies and % will be what individual business are held and the % is the value each business as a proportion of the fund
So your £500 is you investing in a retail store fund (eg M&S Tesco and lidl)
You will buy a slice of the fund at the market value
Say at the time you bought in the total fund value is 1m
your share is £500/£1,000,000 of the fund.
If the fund has 1250000 units (shares) your buy-in of £500 will result in you owning 625 units of the fund
(I am ignoring your £500 by saying you bought existing units in the fund buy in value to do easy maths)
The holdings value of the fund is 1m with a breakdown as follows
300 shares in M&S
200 shares in Tesco
400 shares in Lidl
The total market value of 1m at 9am when trading starts
£500,000 for 300 shares in M&S
£300,000 for 200 shares in Tesco
£200,000 for 400 shares in Lidl
Or fund % is
50% (5k/1m) at £500,000 for 300 shares in M&S
30% (3k/1m) at £300,000 for 200 shares in Tesco
20% (2k/1m) at £200,000 for 400 shares in Lidl
At 11am the market values have changed
£500,000 for 300 shares in M&S
£100,000 for 200 shares in Tesco
£700,000 for 400 shares in Lidl
The total fund value has moved from 1m to 1.3m
Or fund % is
38% (5k/1.3m) at £500,000 for 300 shares in M&S
8% (1k/1.3m) at £100,000 for 200 shares in Tesco
54% (7k/1.3m) at £700,000 for 400 shares in Lidl
Green would indicate a rise in value red a fall in market value.
The fund itself can buy and sell its holdings so may sell off some of the Tesco shares to buy more Lidl shared in the "hope" Lidl shares will rise in value again
If the fund did this they lock in some or all of the the loss 200k from Tesco shares.
Overall you have gained from the market movement but you need to take your cash out (your £500 plus your share of the 0.3m ) to see real money.
You could choose to buy shares directly with M&S Tesco and Lidl but would not be able to decide if/ when it was best to lock in the loss or gain by selling while the investment fund managers have a (littlr) better understanding of the way the markets may move and how the market would value an individual business.
Just to note you are making an investment decision when you give a bank your money. You are giving them a loan and in exchnge it is providing services to manage the in/out flows and it may charge you or pay you a interest amount for the investment transaction.