Can someone remind me what the circled numbers and triangled number mean? Triangle = key frame ? Circle = inbetween ? And number without symbol around ?

generally speaking
letter(layer) + number, one or both optionally circled: genga/keyframe

letter(layer) + number(sometimes with decimals), triangle: nakawari - rough drawing as a reference for the tweens

just number, circled: douga/inbetweens(including cleaned up keyframes)