Congrats for making the convection fan setting! That's one of the trickier ones to figure out. Essentially, the lower the number, the faster the convection fan will spin up to the heat level 6 or so when it maxes out, as Rona said.
Good eye on your heat level settings. They aren't all the same as the factory values, and that also explains your slower conv fan speed at heat level 1. Here are the factory settings, with deviations from yours noted in red.
l1 91
Feed all levels at 100
Ash all level at 9
l2 88
l3 85
l4 82
l5 79
l6 76
l7 73
l8 70
starting fan 80
starting feed 150
stating time 75
igniter time 75
ash dump fan 80
ash dump feed 85
ash dump target 100%
ash dump target level 4 (you didn't provide this value)
TC FOR 25% FAN 50
TC FOR 100% FAN 170
THERMOSTATE HEAT LEVEL 1
LB THRESHOLD % 35
LB FAN ADJUSTMENT 0
LB FEED ADJUSTMENT 20
To determine how almost any given setting works, click on the HELP button in the Bixcheck Monitor, then click on the button that you want help for.