2 150 opening price 2 150 yuan.

The difference lies in the variety of tons and your margin ratio. For example:

Hard wheat 10 ton/hand,

If your margin is 8%, then the capital you need to open a position of hard wheat (long or short) is 2150x10× 8% =1720 yuan!

If your margin is 10%, then the capital you need to open a hard wheat (long or short) is 2150x10x10% = 2150 yuan!

How much money you need depends on the margin ratio given to you by the futures company.

Also, if it's 5 tons/lot, and most varieties in Shanghai are rubber, and the price is 25,000, and the margin given to you by the futures company is 12%, then the capital required for opening a position 1 lot is 25,000× 5×12% =15,000.