This can be stated in active form. Alternate translation: "The priests must determine the estimated values" (See: [[rc://en/ta/man/jit/figs-activepassive]])
There were shekels of different weights. This is the one that people had to use in the sanctuary of the sacred tent. (See: [[rc://en/ta/man/jit/translate-bweight]])
The purpose of this sentence is to tell how much the sanctuary shekel weighs. The gerah was the smallest unit of weight that the Israelites used. Alternate translation: "One shekel must equal twenty gerahs" (See: [[rc://en/ta/man/jit/translate-bweight]])
If it is necessary to use modern weight units, here is a way to do it. Alternate translation: "One shekel must weigh ten grams" (See: [[rc://en/ta/man/jit/translate-numbers]] and [[rc://en/ta/man/jit/translate-bweight]])