How relocations designed in fasm1?

In fasm1 at assembly stage any operand as variable/constant/label presented by 20 byte structure

Code:

virtual at 0
        expr@opnd.value           dq ?
        expr@opnd.reg1            db ?
        expr@opnd.reg2            db ?
        expr@opnd.regamount1      db ?
        expr@opnd.regamount2      db ?
        expr@opnd.value_type      db ?
        expr@opnd.value_sign      db ?
        expr@opnd.unknwn14        dw ?
        expr@opnd.unknwn16        dd ?
        sizeof.expr@opnd = $
end virtual
label   expr@opnd.regs            dword at expr@opnd.reg1
label   expr@opnd.reg.items       word at expr@opnd.reg1
label   expr@opnd.reg.amounts     word at expr@opnd.regamount1

When file format is relocatable information about isrelocative or not stored in "expr@opnd.value_type" member of this structure (suppose in bit 1, but I could wrong).
Tomasz, could thou explain meaning of different value_types - for what cases each other? how works "relativeto $"
smallest relocatable I could imagine with "relativeto $" construction is

Code:

format PE
if 0 relativeto $
        display 'not relative'
end if
data fixups
end data

for 0:
all 20 bytes structure is zeroed.

for $:
[expr@opnd.value] holds $00401000 (constant offset part of $)
[expr@opnd.regs] holds 0 (because it isn`t relative to any regs)
[expr@opnd.value_type] - here is magic (for me magic, suppose 1st bit set)
[expr@opnd.value_sign] holds 0 (it could have only 2 values -1 & 0)
[expr@opnd.unknwn14] - I even give up to properly name it no idea what it for
[expr@opnd.unknwn16] - suppose it is ptr to internal(compilation time) symbol table, but what value would be here in case of $ I don`t know.
And in case of "relativeto" operation must be matched only (expr@opnd.regs & expr@opnd.value_type) or expr@opnd.unknwn16 too?

for other relocatable file formats

Code:

format MS COFF
if 0 relativeto $
        display 'not relative'
end if

Code:

format COFF
if 0 relativeto $
        display 'not relative'
end if

Code:

format elf
if 0 relativeto $
        display 'not relative'
end if

In these cases 20 bytes structure for $ differs from same one from PE by zeroed expr@opnd.value member. Are other field members are differ? or differ only internal symbol structure pointed with expr@opnd.unknwn16.

(maybe expr@opnd.value_type interfere in some manner with "type of symbol (table 5.3) from Table 5.1 Symbol structure from fasmguide.zip\tables.txt" and expr@opnd.unknwn16 interfere in some manner with "address of object section or external symbol to which this symbol is relative from Table 5.1 Symbol structure from fasmguide.zip\tables.txt")
Thanks in advance.