The next shortest slot on an infant seat that I measured was the Maxi Cosi Pico at 6 1/2" (the Safe Seat was 6"). I was personally surprised to see the measurement of the Keyfit - with the infant padding in, the lowest slot measured 7 1/2". I have always heard that the Keyfit is a good seat for smaller infants so I guess I expected the slots to be shorter.
Here is a list of the seats I measured slots on:
Graco Snugride slots 8", 10 1/2"
Graco Safe Seat 1 slots 6", 8 1/4", 10 1/4"
Peg Perego Primo Viaggio lowest harness position 6 3/4", top 10"
Chicco Keyfit 30 lowest slot w/infant padding 7 1/2", without padding 8 1/4", 10 1/4", 12 1/4"
Maxi Cosi Pico slots 6 1/2", 7 5/8", 8 5/8", 9 7/8"
Baby Trend Flex Loc lowest slot 8"
Graco Safe Seat 2 top slot 15 1/2"
Graco Comfortsport top slot 13 3/4"
Cosco Apex top slot 17"
Evenflo Titan Elite top slot 14"
Evenflo Tribute 8", 12", 14 3/8"
Evenflo Triumph Advance top slot 17 1/2"
Cosco Alpha Luxe 3 in 1 top slot 15 1/2"
Eddie Bauer 3 in 1 top slot 15 1/2" - 15 3/4"
Maxi Cosi Priori top slot 15 1/2"
Britax Roundabout top slot 15 1/2" - 15 3/4"
Britax Diplomat top slot 15 1/4"
Britax Marathon top slot 17 1/2"
HTH!