Memory representation of floating-point numbers:

• $4$ is the memory size in bytes, not bits ($1\text{ byte} = 8\text{ bits}$).
• $7$ is approximately the number of decimal digits of precision.
• standard IEEE-754 single-precision floating point number (REAL*4) occupies exactly $4\text{ bytes} = 4 \times 8 = 32\text{ bits}$ (comprising $1$ sign bit, $8$ exponent bits, and $23$ mantissa bits).
• $22$ is incorrect.