Partial payment of salary in particular month

[silverTR]

Hi Folks
I d like to ask for your precious advices about my case.
I have 12 months of payslips all the same .. Only one month , my company made the payments partially and because they made a delay , they awarded us like +100 pounds.
So lets say i am having £1000 , during march statement my salary record is like £800 and £300 total 1100..
How can i explain this to home office ? Any ideas.