Solution

1. Go to Contracts >> Click on Contract Types.
2. Select the Contract Type to make hours and minutes appear on invoices >> Click on to edit.
3. Click on the Contract Charges tab >> Tick Show per hour charges as hours and minutes on invoices rather than total minutes, located in the bottom right hand corner.
4. Select Save    
5. Any invoices raised under that Contract Type will now show with hours and minutes where relevant as per the below invoice.