In a tetrahedral structure, the ideal bond angle is 109.5 degrees. However, with one lone pair, the actual bond angle is typically slightly less due to the repulsion exerted by the lone pair, which pushes the bonding pairs closer together. In this case, you mentioned that the bond angle is 107 degrees.
To find the difference between the predicted bond angle (109.5 degrees) and the actual bond angle (107 degrees), we can calculate:
\[ \text{Difference} = 109.5^\circ - 107^\circ = 2.5^\circ \]
Therefore, the difference between the bond angle predicted by the geometry and the real bond angle for this compound is 2.5 degrees.