I have to change my laptop's battery's "Last Full Charge" value. Is there any software through which I can do this or is there any software through which we can change battery firmware's parameters?
It should be set again if you disconnect the charger for a bit, (long enough to restart the charging cycle) and reconnect it. Depending on where you are in the charging cycle, you might have to do it twice.
If you want to recalibrate the charge level, you should discharge the battery completely (please take care not to trash your filesystems at the same time, and remember to avoid hibernating at low level and the like). Then remove the battery, connect the charger, boot the computer and reconnect the battery to let it recharge.
If what you wanted was to set the Last Full Charge value to some arbitrary number, I guess you have a bit of low-level programming in front of you, as well as a hunt for interface documentation.