Hello and apologies if my question is rather naive.

My setup is Guitar / Line 6 Helix / AudioBox iTwo / Studio One (Windows).

iTwo setup:

Either channel - the behaviour is the same in both cases
Input Source set to line level
Input gain control set fully anti-clockwise
Monitoring on headphones
Monitor mix set fully anti-clockwise (i.e. direct)
Main output knob set fully anti-clockwise (i.e. zero)

I'm new to home recording and I was recently experimenting with setting levels. I found that even with the iTwo channel's Input Gain control set to its lowest level, it's possible for me to set the Helix output to sufficiently high a level as to cause distortion in the iTwo.
Under these conditions I am still able to clearly hear the distortion even though the channel's Input Signal Indicator is only flickering green.

It's not a huge deal to me since I can just reduce the helix output and there's still enough signal into Studio One to keep the input level where I need it to be. I'm just interested if anyone can explain what's happening?

The manual has this to say:

Power User Tip: Never run your input levels higher than the channel
inputs can handle. If you overdrive the analog-to-digital converters, it will
cause digital distortion (digital clipping), which sounds terrible.

Given the above, I kinda expected that with the input gain set to its lowest level I wouldn't be able to produce distortion in the iTwo.

Is it likely that I'm just overloading the iTwo's preamp, even with the input gain set fully clockwise?

TIA - as I say, I'm just interested