Seeking Assistance with adjusting minimum speed on CNC3018 pro

[RioAtJapan]

Hello

I am currently using the "Grblcontrol (candle_1.1.7)" software for my CNC3018 pro (Mostics). I have configured the following setting in the console box:

$1=25　$2=0　$3=3　$4=0　$5=0　$6=0　$10=1
$11=0.010　$12=0.002　$13=0　$20=0
$21=0　$22=0　$23=0　$24=25.000
$25=500.000　$26=250　$27=1.000
$30=1000　$31=0　$32=0
$100=800.000　$101=800.000　$102=800.000
$110=1000.000　$111=1000.000　$112=600.000
$120=30.000　$121=30.000　$122=30.000
$130=200.000　$131=200.000　$132=200.000

With these setting, when I send the G-code G1 Z-10 F3, The Z-axis moves downwards at a rate of 3mm/min, which is as expected.

However, when I issue the command G1 Z-10 F2, The Z-axis moves downwards at a rate of about 2.3mm/min, which is not the expected 2mm/min.

In an attempt to lower the minimum speed, I adjusted the $112 from 600 to 60. Despite this change, the lowest achievable speed remains at 2.3mm/min.

I apologize if this question has been asked before or if the answer is readily available. I would greatly appreciate any insights or suggestions on how to effectively decrease the minimum speed.
Thank you in advance for your time and assistance