To fix this problem, both leaderboards need to be running on different columns, even if the scores are the same.
To avoiding entering scores twice, you can set the value of the new score column to equal the value of the original score column with a formula.
First, in your google sheet, add the header for the new score column:
Then, set a formula for the first cell in the new column (C2) by selecting the cell, and pressing '=':
Then click the first cell in the original column:
And press 'Enter' to finish setting the formula:
Next, click and drag the fill handle (blue square in bottom right of cell C2) down the column to apply the formula to the rest of the cells:
Now whenever the scores are updated in the Score A column, the Score B column will also be automatically updated.
Once the sheet is set up, go into Spinify and edit the two leaderboards that previously used the same score column in your google sheet so that one leaderboard uses Score A and the other leaderboard uses Score B.
Now your google sheets achievements will only fire once.