A VSP opcode is an 8-bit byte, but the table contains only 128 entries. The LSB of the opcode indicates the form of the instruction : either short (16 bits) or long (32 bits with a 16-bit immediate). The instruction itself does not change (or so little) with the short/long flag, so both versions of the same instruction are covered in the same box.
The instruction's "form" reflects the semantics of the instruction. It is the assembler's view of the encoding.
The flags contain the informations used by the assembler to transform the semantic into an encoded binary word.