I’m glad it helped 
Before answering about that mysterious EG AMT knob, let me try something to unveil the modulation sections secrets to you.
In a nutshell, a sound is defined by a pitch (i.e. the note), a timbre (i.e. the character of it) and an amplitude (i.e. the volume).
In a nutshell, your favorite substractive synth implements this principle: the oscillators are raw timbre generators that the filter can tame to achieve softer timbres. The pitch is determined by the key you press and some octave/oscillators frequency settings. The amplitude is determined by a (voltage controlled) amplifier.
Things can ge boring quite quick with just that. They becomes much more interesting, expressive when all those parameters are modified in real time, e.g. by playing with the knobs. But you need your hands for playing the keys… so only one hand remains for all those knobs!
That’s where modulation enters: modulation is like a bunch of hands moving the knobs for you, that is: modifying the parameters for you.
The LFO, for example, is like a hand moving some knobs periodically, with a given pattern and at a given rate.
The envelopes control the parameters in 4 phases: an attack time for going from zeo to the max level, a decay phase for going from there to a sustain level, and then a release phase that starts when you release the key, for going from the sustain level to zero. “Level” of what, should you say? Level of whatever you route this envelope to. The amp envelope is routed to the amplifier, hence controlling the volume of your sound. The filter envelope is routed to the filter cut off frequency.
EG AMT stands for Envelope Generator Amount: this knob allows you to decide how “deep” the envelope would “turn” the knob for you, and in what direction, that is: the modulation amount of the filter cut off frequency by the envelope. This modulation “circuit” is permanent, i.e. you will always be able to control the cut off frequency with the filter envelope.
In the Modulation section, on the contrary, you can connect various sources (= supplementary hands) to various destinations (= parameters whose knobs you xant to move) and decide the amount of modulation (= how much the hands will tunr the knobs for you). That’s called: configuring a modulation bus. Also, the modulation wheel is always controlling the global amount of aaaaallll that.
Hopes this make sense 
Consequently, in the situation we discussed before, if you set this EG AMT knob to anything different from zero, the filter envelope will modulate the filter cut off frequency accordingly. Remember that you previoulsy routed the filter envelope to the oscillator 2 pitch; so it means that this envelope will modulate both paramters, that’s all 
To get familiar with modulation, try to set up the modulation bus to modulate the oscillators pitch: that’s the most obvious parameter to hear the effect of various sources.
Bon voyage! 