In a tetrahedral molecular geometry, the ideal bond angle is 109.5 degrees. If a compound has one lone pair and three single bonds, it adopts a trigonal pyramidal shape, which experiences some repulsion from the lone pair, resulting in a bond angle less than 109.5 degrees.
In your scenario, the real bond angle is 107 degrees. To find the difference between the predicted bond angle (109.5 degrees) and the actual bond angle (107 degrees), you can subtract:
109.5 degrees - 107 degrees = 2.5 degrees
Therefore, the difference between the bond angle predicted by the geometry and the real bond angle for this compound is 2.5 degrees.