Bolt length

Dear all
i have a flange connect with valve on spec /B01 (Bspec /B03-BOLT)
- Flange: Blrfarray /BTSE_150FLAN:50
- Valve:  Blrfarray /BTSE_150FLAN:50
- goto /BTSE_150FLAN:50
   --> BLTP:
   Attributes     Name /BTSE_150FLAN:50-4
   Type BLTP
   Lock false
   Owner /BTSE_150FLAN:50
   Description unset
   Number 4
   Bdiameter ( 16 )
   Btype BOLT
   Bthkness 45
i don't know why on isometric BLEN is 95 ( not Bthkness * 2)
Please refer :
- Bspec /B03-BOLT:
Bltref /new.SBOL.B16

- Name /new.SBOL.B16  Type SBOL
 Lock false
 Owner /new.BOLT.SBOL
 Nstdblength /new.BOLT.DTAB
 Bdiameter ( 16 )
 Length 0mm
 Noff 0
 Xtralength 0mm

-Name /new.BOLT.DTAB
Type DTAB
Lock false
Owner /new.BOLT.LTAB
Blength (60mm 65mm 70mm 75mm 80mm 85mm 90mm 95mm
100mm 105mm 110mm 115mm 120mm 125mm 130mm 135mm
140mm 145mm 150mm 155mm 160mm 165mm 170mm 175mm
180mm 185mm 190mm 195mm 200mm 205mm 210mm 215mm
220mm 225mm 230mm 235mm 240mm 245mm 250mm 255mm
260mm 265mm 270mm 275mm 280mm 285mm 290mm 295mm
300mm 305mm 310mm 315mm 320mm 325mm 330mm 335mm
340mm 345mm 350mm 355mm 360mm 365mm 370mm 375mm
380mm 385mm 390mm 395mm 400mm 405mm 410mm 415mm
420mm 425mm 430mm 435mm 440mm 445mm 450mm 455mm
460mm 465mm 470mm 475mm 480mm 485mm 490mm 495mm
500mm 505mm 510mm 515mm )
:MESCNO1 unset
:MESCNO2 unset
:clienta1 unset
:clienta2 unset
:clienta3 unset
:clienta4 unset
:clienta5 unset
:clienta6 unset
:clienta7 unset
:clienta8 unset
:clienta9 unset
:clienta10 unset
:clienta11 unset
:clienta12 unset
:clienta13 unset
:clienta14 unset
:clienta15 unset
:clienta16 unset
:clienta17 unset
:clienta18 unset
:clienta19 unset
:clienta20 unset
:OLD_STOCK NA
:STOCK_PATT NA
:DESCR unset

:) may be with thickness of gasket : 2mm, so blen 95