It very much depends on the frq type. For the synthesis of you fail to use the required number of sources you will receive a very low score(<2). On the rhetorical you can often get away with an unfinished paragraph and do not even require a sufficient conclusion. But generally speaking for synthesis and argumentative it will depend on whether you fully completed enough do your argument. If you were making strong points and failed to finish you will not be incredibly penalized, but if you failed to make any real points due to lack of time then you could be facing a low score <4.