2 pointsCooler liquids retain more gas than warmer liquids. If your temperatures remained low your beer retained more CO2 from fermentation than it would have if warmer. Starting with a higher carbonation level you need less sugar to reach the final carbonation level desired.
2 pointsrick my glass hydrometer is from when i first started brewing ages ago... it hasnt killed itself yet. the only piece of original equipment to commit suicide was my bottling wand... and it was plastic. while removing the tubing i heard SNAP.. sadness. i find that by singing to my hydrometer as i lovingly unwrap it for use... and when i clean it, that it stays happy and healthy.
1 pointOne final comment from me on this topic. If you are wondering why the MrBeer directions have so much sugar recommended remember their target customers are new brewers. If the kit is placed on a kitchen counter top with ambient air temps at the upper end of the recommended range, the higher priming rate will compensate for the CO2 off gassing during fermentation. The down side is, the fewer brewers who do keep theirs on the cooler end risk gushers. When those guys turn to this forum, it's unfortunate that our first thoughts some times jump to conclusions of incomplete fermentation or infections.