Here is a visualisation of how the Spare votes replaces wasted votes with votes for qualitying parties. It is based on 2020 General Election results
See how the wasted votes at bottom left are al;ost all replaced by intentional votes for qualifying parties at the right.
Data on the left is from 2020 General Election results. The transfers are just guesses ro show how second choice works.
Two-choice party voting or The Spare Vote 