It could be possible that kill rating takes into consideration healing (how you were killed). Gather supplies and outwit your opponents to become the last person standing.

How you play in one mode will not affect your ranking in others! PUBG Mobile states that “Survival Rating is determined by your ranking in each match, Kill Rating is determined by the number of kills you made/how you were killed in each match”. Also, when you get killed, we give you the stats on who killed you! In this tier, there are 5 sub ranks. Different Ranking per Game Mode. PUBG Mobile takes a lot of cues from the PC version of PUBG, but every now and then it's the other way around.

There are separate rankings per each game mode, as well as between FPP and TPP settings. The list of 8 ranks ranging from lowest to the highest are – Bronze. PUBG Mobile is the FREE battle royale shooter that pits 100 players against each other in a struggle for survival. How to Check Your Rank

We have released an awesome in-game overlay app that allows you to track your stats, as well as the stats of your friends!
PUBG Mobile ranking system is divided into eight broad ranks and five sub-ranks in each rank below ‘Ace’. So, there’re overall 6 X 5 = 30 + 2 = 32 ranks in PUBG Mobile game.

PUBG Mobile's ranking system is based on a player's total ranking in matches so keep playing to get higher up the ladder.