the amount of bkr lost/gained depends on several factors :

• the difference in bkr between the 2 players
  
• the amount of games played by the player
  
• the variation in winning/losses (deviation)
  
• and maybe some more factors?
  

i assume you are talking about your game of jungle with volant ? as you had not played a game of jungle before your bkr was at 1500 (i think?) which was more than 400 points lower than volants bkr at that time ... 400 seems to be a break point .. when the difference is more than 400 the gain/loss in bkr is even larger