It's been a while in the making but the Efficiency system has undergone some much needed changes. The efficiency values have been removed entirely. This was causing confusion in the gardening community where many gardeners thought the number represented actual cross chance percentage (which was not the case!).
The icons have also been updated to reflect these changes as well as to accommodate colorblind users. There is now a green circle, yellow square and red hexagon to represent how efficient a cross is.
Most efficient; use any (preferably higher in the list)
Can become costly and/or time consuming; use if no green available
Very expensive & time consuming; avoid at all costs
The crossbreed table will still automatically sort by Efficiency with the most efficient crosses being listed at the top and least efficient at the bottom. But as always it's best to do some homework before committing to a cross as there are many variables involved that can change depending on current supply and demand.
For more in-depth explanations see the Site Documentation page.