What are the ramifications of the statement "ve'Chol Erk'cha Yih'yeh be'Shekel ha'Kodesh"?
Rashi: It means that wherever the Torah mentions 'Shekalim' in the current Parshiyos, it means a Shekel ha'Kodesh - a Sela, which is equivalent to two Shekalim.
Torah Temimah (citing Erchin, 7b): It means that the minimum assessment in the current Parshiyos is one Shekel ha'Kodesh. 1
Tora Temimah: If for example, a poor man cannot afford to pay Hekdash the Erech of the person whose Erech he declared, then the minimum that the Kohen assesses him for is a Shekel ha'Kodesh (See Torah Temimah).
How much is twenty Geirah?