fee formula for multiple selections of field type list

Hello,
I have set up a Custom Field of type 'list'.
I have set 'Multiple' to 'Yes' to enable multi-select.

I have set the Options Value to
Donation (Specify below)
Silver Donation (£150)
Gold Donation (£250)

I have left Options Text blank.
I have left Default Values blank.
I have set Fee Field to Yes
I have set Fee Values to
0
150
250

I have left the fee formula blank.

When the user selects just one option, the Total Amount field is correctly set with the appropriate value.

But when the user selects more than one option, the Total Amount field is just set to one option.
In my case, if both silver and gold are selected, the amount is always 150, regardless of the order in which they were selected.

Do I need to adjust the fee formula to enable multi-select ?

Thanks

Hello

You should not have to setup Fee Formula. Could you please submit a support ticket sending us link to the form, tell us ID of the custom field so that I can check to see what's wrong and guide you to correct it

Regards,

Tuan