What is 16 bit word's equivalent in decimal?

Question

Question:

For a 16 bit word with 6 bits for an opcode

• How many different instructions could I fit into the instruction set?
• What is the largest number that I could use as data?

Answer:

• Number of instructions: 2⁶ = 64
• largest operand: 2¹⁰ - 1 = 1023

Source

My question is how did they calculated 2¹⁰ from 16 bit word?

Answer 1

If a number takes up 16 bits, and you use 6 of them for something, that leaves 10 bits.