Quickleaf
Legend
Yeah, you'll want to go well beyond the Deadly threshold in the DMG for one encounter if that encounter is meant to be your only encounter. 4x-5x would fit with the idea of doing 4 to 5 deadly encounters in a row, which would be more in line with upping the value to be worth 4 or 5 encounters for a whole day.
Well, according to Kobold Fight Club, my 3 carrion crawler anecdote was worth 2,025 adjusted XP, versus a DMG-calculated Deadly lower end threshold of 1,200 XP.
By the way, looking at the amount of monsters (in terms of sheer XP) that you need to throw at the PCs to get a Deadly fight and (at least at level 2) it's like practically leveling up the party. Does this persist throughout higher levels too? Or is it exclusive to low levels (e.g. 1-3 or 4)?