Decimals are just a way of saying you want a fraction of something, just like normal currency. If you have $0.997685 USD, you have a little more than 99 cents, but USD doesn't count that far in regular dealings. So we say $0.99 or $1 if rounding up. With bitcoins, since the value will/should increase over time as usage/value increases, 0.000001 bitcoin could be worth $1 in the (far) future.

Also, a period would have been nice.