3/6NL FR: River Overbet???

[mecha]

villan in this hand is 29/6/2. what does his river overbet represent here??? Also where did I misplay my hand? Also, easy all in on the river or do i even think about the quads?

No Limit Holdem Ring game
Blinds: $3/$6
9 players


Stack sizes:
UTG: $577.40
UTG+1: $328.05
MP1: $136.35
MP2: $451.40
MP3: $619.20
Hero: $1309
Button: $667.05
SB: $734
BB: $234

Pre-flop: (9 players) Hero is CO with
UTG folds, UTG+1 calls, MP1 calls, 2 folds, Hero calls, Button calls, SB calls, BB checks.

Flop: ($36, 6 players)
SB checks, BB checks, UTG+1 checks, MP1 bets $6, Hero raises to $20, Button folds, SB calls, 3 folds.

Turn: ($82, 2 players)
SB checks, Hero checks.

River: ($82, 2 players)
SB bets $250

Results:
Final pot: $582

[shobute]

[Zmej]

[Danhdan]

[ua1176]

[Zmej]

[Zmej]

[shobute]

[black_knight6]

[adamh]

i shove, you prob split with the other J

[ua1176]

[black_knight6]

[GodlikeRoy]

[black_knight6]

[GodlikeRoy]