Binary Floating Point Range/Precision for 4-bit Mantissa and 4-bit Exponent
Yes, that is correct. Your mantissa has only three magnitude bits, so you can only represent numbers from -8 to 7, multiplied of course by any power of 2 from $2^{-8}$ to $2^7$. 11 is impossible to represent, because any positive exponent gets you multiples of 2, any negative exponent gets you numbers less or equal to $7*2^{-1}=3.5$, and exponent 0 is just numbers from -8 to 7.