Translation:Did you notice that the lecture was quite short?
Mi uzus "iom" aŭ "relative" anstataŭ "sufiĉe", ĉar la radiko "sufiĉ" havas klare alian sencon. Laŭ PIV: Estanta en tia kvanto, kia estas bezona
An English speaker would only say this to someone if they felt that a lecture was briefer than the speaker expected; ‘It was very short.’ (with a tone of curiosity and unexpectedness. If I wanted to tell someone that it was ‘short/brief enough’, I would tell them, ’The lecture was appropriately short; just short enough.’ or something very similar to that.