There are 2 types of bonuses: Active and Passive.

An active bonus is there to motivate to hit a target. You clearly felt your £1500 target was one.

A passive bonus is just a little bump that serves to reward employees when the company does well - you'll either get it, or you don't, regardless of your drive and intent. Clearly the £250 one has now become this.



Therefore, I would accept that you might end up with a little extra, you might not, doesn't really matter. In many ways, it would be better if you don't. That would send the signal that the amount offered no longer has the effect of motivating staff, and should encourage them to learn from their mistake.