1. Momentariness 刹那滅. Seeds pass out of existence each moment, and produce corresponding new seeds which endure for one moment and then pass out of existence, producing corresponding new seeds, and so on. Seeds must be momentary because that which is eternal is incapable of producing. A corollary of this is that any factor which is uncaused is eternal. 〔順正理論T 1562.29.533c18〕
2. 果倶有 Seeds must be simultaneous with their manifestations. This refers the aspect of seeds bringing about effects that are simultaneous with their causal basis. For example, all three legs of the tripod serve as the causal basis for the standing upright of the tripod. The effect of the causal contribution of the three legs of the tripod—its standing upright — is simultaneous with the causal basis—the three legs. This aspect of seeds is related to their causal capacity 功能 of simultaneous causation 倶有因 it its two aspects of simultaneous causation bringing about an effect though collective action 互爲果倶有因 and simultaneous causation with a singular effect 同一果倶有因. The tripod is an example of the former. The latter occurs when two or more things collectively support one thing. The Foguang Dictionary gives the example of multiple columns collectively supporting one roof. 〔大毘婆沙論T 1545.27.81b9〕
3. 恆隨轉 Seeds form a uninterrupted series 無間相續. In the Cheng weishi lun, this aspect of seeds features in arguments for the existence of ālayavijñāna 阿賴耶識, in that the forthcoming layers of consciousness 轉識 do not form a continuous series, and hence, cannot support the regeneration of seeds 〔成唯識論 T 1585.31.9b18〕
4. 性決定 Seeds must have the same karmic moral quality as their manifestations, whether wholesome 善, unwholesome 不善, or indeterminate 無記.
5. 待衆緣 Seeds can only exercise their causal efficacy when they meet with the appropriate causes and conditions. While seeds pass into non-existence after they deplete their causal efficacy to perform a specific action, the regenerated seeds that replace them retain the causal capacity to initiate action as a function that can be accomplished in the future.
6. 引自果 Each seed must produce its own specific manifestation and no other. For example, if one plants a rice seed, one expects it to grow into rice sprout, whereas if one plants a barley seed, one expects it to grow into a barley sprout. These are defined in the Commentary to the Summary of the Great Vehicle and in the Cheng weishi lun. See Wei Tat (1976, 126–129). 〔攝大乘論釋 T 1597.31.329b28-c10〕

References:

La Vallée Poussin, Louis de, trans. 1928. Vijñaptimātratāsiddhi: La Siddhi de Hsuan-tsang. Paris:  Paul Geuthner.

Wei, Tat, trans. 1973. Ch'eng Wei-Shih Lun: The Doctrine of Mere-Consciousness. Hong Kong:  Ch'eng Wei-shih Lun Publication Committee.