The principal paragraph here draws on John Philoponus, Commentary on Aristotle's de anima 98.23-34 Hayduck; the second switches to a military handbook.
[1] These 'four modalities' of change are based, in a very general terms, on Aristotelian positions, and coincide with change, as it is examined under the category of substance (corruption), of quality (alteration), and of quantity (growth), as described in the following line.
[2] This describes in general terms Aristotle's doctrine of change, as it is expounded in detail in Physics 1.4-7. Aristotle puts forwards three principles of any change (both substantial – generation-corruption – and relative – alteration or quantitative change: growth and diminution): (1) the substratum or what underlies any change (which identified with matter), (2) privation, the negative determination the 'thing' in process of change has before acquiring the positive determination or (3) form, which turns out to be that for the sake of which the process of change is done. Both privation and form are assumed to be contraries, and the change is understood as a process going from a contrary ('not pale') to the other contrary ('pale'). The same thing can be applied in cases of 'substantial change', such as what goes from an entity to a non-entity (corruption), or what goes from a non-entity to an entity (generation; see Physics 224b35-225a11). Even in the cases of substantial change or generation without qualification (ge/nesis a(plh=) there must be something underlying, i.e. a substratum.
[3] cf. in brief Polybius 18.30.4.
[4] For klisis see generally kappa 1816, kappa 1817. That this metabole is a 'double' klisis implies a standard turn of 90 degrees to right or left.
[5] Since the spear was carried in the right hand and the shield on the left arm, these are standard terms (from the fifth century BCE onwards) for right and left.