I would guess that the values in that column with no -ve or +ve can be taken as positive. Since the dome or dish/reliefs modify the crown, I think we can safely say by now that if it's adding to the crown volume it's a positive value and taking away volume then it will be negative. These values are used in the formula for working out the CR, so I assume (without knowing for sure) that there might be a value allocated as a constant for a totally flat top piston that is perfectly level with the deck.
Assuming is dangerous. Pick out a calculator you like, and study how it wants the values entered. The numbers asked for will tell you whats important. Deck height, how far a piston is down in the hole, or not, has a HUGE effect on compression ratio.
For example, my old trw book lists two 340 pistons, 2316 with a minus 7.5ccs for the valve reliefs, with a comp.height of 1.84. Also lists 2322, 10.7cc dome, ch of 1.839. You can calculate where those pistons would be in a blueprinted deck, but until you measure, in YOUR block, calculations are garbage.
Edit. Yes, a perfectly flat top piston, at perfect. 000 deck, has a value for deck height volume.......zero. That situation almost never happens.
2nd edit. Those trw 340 pistons referenced above....the flattop weighed 720-750 grams, depending on overbore. The domes were 662-680, with a 250% tighter weight + or - tolerance. Both used a 154 gr pin. (Both were forged pistons).
Worst case scenario.... 900+grams, plus rings and pin clips.
