Number:

0xxxxxxx : 7 bit
10xxxxxx xxxxxxxx : 14 bit
110xxxxx xxxxxxxx xxxxxxxx : 21 bit
1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx : 28 bit
11110000 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx : 32 bit
11110001 \
     ...  > reserved
11110111 /
11111yyy : 3 bit

Where:
    xx...xx will be extended preserving sign (if any)
    yyy will be extended as well and subtracted from MAX_VALUE

String: