Not every hand has to have both blinds. In some games, when the BB from the previous hand leaves the table, the SB becomes dealer and there is no SB for the next hand. I think that's what you're seeing here.
So although the game is normally 5/10, for this hand there's only a single 10 ante by player 1.
Looking at the game preceding this one in the database, indeed 'num' was present and in SB position, while the other players (including the BB) were different. So that's at least consistent. It means that the new player 'Carcass' would have to post the BB, while 'num' was allowed to play without posting a blind.
ETA: I've confirmed this now. I checked and every time a game is played with a single blind, the previous game's big blind is no longer at the table. So a single blind game is just a side effect from how the button and blinds move after players leave.