Carly, to me it sounds more like a problem of imagining a problem that would lead to this situation (rather than anything grammatical or so). -
Just image somebody living in a rented flat, having to pay the rent on a monthly basis.
Now, in March/April, due to excessive rain, water penetrates into the flat, say, from underneath the window-sill.
The tenant informs the owner and asks the rent to be shortened by 10% for as long as the problem is not 'fixed'.
As the Landlord does not react, the tenant, in desperation, stops paying the rent altogether as of June!
That makes the Landlord threatening the tenant to take him to court. -
Eventually, the tenant writes (in August):
'If you get that problem fixed and agree to a 10% reduction in rent (for the period while the fault lasts, i.e. April to now), we'll back-pay the rent as of June. . .
Hope, this makes the set-up 'nachvollziehbar' . . . ;:-)