There are two parts to this problem. The first is to figure out what voltage ranges are possible and the second is to use the digital representations of the voltages to compute what values were digitized.

"5 V full scale" could have any of 3 meanings: 0 to 5 V (unipolar), -5 to 5 V (bipolar), and -2.5 to 2.5 V (bipolar, total range 5 volts). Sloppy wording in describing data begets sloppy interpretation.

For each of the 3 numbers, we have 3 number systems that may be employed (after all, even if the data are unipolar, two's complement binary coding or signed magnitude coding could be used). For unipolar interpretation, the most significant place has a value of 2.5 V, while the least significant place has a value of 2-8 * 5 V = 5 V/256 = 19.53 mV. For either of the signed encodings, there are only 7 magnitude bits. The most significant bit has a magnitude of either 2.5 V (-5 to 5 V range) or 1.25 V (-2.5 to 2.5 V range). The least significant bit has 2-7 * 5 V or 2-7 * 2.5 V magnitude = 39.1 mV or 19.55 mV.

For each entry, the binary number was translated to decimal in the row labeled "value." When the range can not include values <0, any code that would be interpreted as negative is meaningless.
Otherwise, (number)/(maximum coded value) * (voltage range for the same sign as the number) gives the answer shown.

Range 0 to 5 V
0110 0011 1110 0100 1010 1001
Number System
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
Value
 99 99 99
 228 -100 -28
 169 -41 -87
Voltage
 1.934 3.867 3.867
 4.453 Meaningless Meaningless
 3.301 Meaningless Meaningless

Range -5 to 5 V
0110 0011 1110 0100 1010 1001
Number System
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
Value
 99 99 99
 228 -100 -28
 169 -41 -87
Voltage
 3.867 3.867 3.867
 4.453 -3.906 -1.094
 3.301 -1.602 -3.398

Range -2.5 to 2.5 V
0110 0011 1110 0100 1010 1001
Number System
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
 Straight Binary Signed Magnitude Two's Complement
Value
 99 99 99
 228 -100 -28
 169 -41 -87
Voltage
 0.967 1.934 1.934
 2.277 -1.953 -0.547
 1.651 -0.801 -1.699