A binary number consists of bits, but the computer can organize these into bytes just as it does for characters. If we wrote the integer 65 as a binary number, it would look like 01000001. The computer could do arithmetic with this number. So 01000001 can be either a number or a character. Numbers can occupy any of the possible byte values , so it takes all eight bits to work with numbers.
Instruction code is what tells the computer what to do.
Computer code also contains data, since 01000001 could also be part of a memory address. Code also uses all eight bits. So the bottom line is that non-character data use eight bits, code uses eight bits, the full character set uses eight bits, but the keyboard characters only use seven bits. But let's say you had to pay by the bit. You might decide that seven is enough.