My apologies, having booted Acad 17 and seeing for myself, looks like I got the wrong end of the stick. Not quite, though!
DYNMODE (0 or 1) turns Dynamic Input on or off and can be controlled with one of the tiny buttons on the bottom of your screen. This is your problem fixed and was probably caused in the first place by a careless click.
If DYNMODE is Off(0) then the value of DYNPICOORDS is irrelevant. If DYNMODE is On then DYNPICOORDS controls whether typed input at the cursor is relative to 0,0 (absolute) or to the last point (relative). Basically it just adds a '@' to whatever you type.
This 'dynamic input' thing seems to be the default out-of-the-box setting for at least the last few Releases, but I've never seen it because usually, whenever I install Acad (had my own copy since 2007, been setting it up since mid-90s) the very first thing I do is go through the Options pages looking for just this kind of thing to disable.
Eg: Dynamic input, Polar tracking, Selection Previews (try moving a mouse over 10,000+ objects without you or acad having an epileptic seizure), Command prompt-at-cursor, scroll bars, US english dictionaries, non-classic modeless Layer & Xref commands, small crosshairs, auto-snap magnets, and probably a fair few more.
This has been habit because:
1. long ago, when these sorts of 'visual aids' started appearing, they would quite happily bork your session, and it's not like Autocad ever needed much encouragement to crash! I use a lot of 'heavy' DWGS: Lots of xrefs, lots of 3D and all loaded up together: Architecture, Structural, pipes, ducts and cable trays.
2. they usually slow me down or else make me use the mouse more instead of the keyboard. I still don't use the Ribbon in Acad for this reason. I do in Revit, but only if I don't have a 2-letter keyboard shortcut. RSI would be the end of my career.
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Intel 7740x - Quadro 6000 - 32Gb RAM - CADmouse - Logitech G710