Question about LP gain/loss calculation

So i started playing league closeish to the end of season 6, and in season 7 have been trying to climb the ranked ladder because it is more competitive and challenging than normals.

Got placed bronze 5 for season 7 as expected.

Just recently i won promotion (for the 3rd time) to bronze IV.

Now here's where my question comes in, all the times i've gotten into B4, including this one, my LP gains for wins are far lower than my LP loss for losses.

For example, Since getting promoted this time I've won 3 games, and gained 13 LP for the 1st 2 wins, and 12 LP for the 3rd win, I haven't lost this time around in B4, but if its anything like the last 2 times, I'll be losing 20+ LP per loss, which can make it tough to climb especially when a lot of the same teammates from bronze 5 are showing up.

Now I am not complaining about this or anything, I don't mind the grind of climbing, I am just curious how Riot Calculates what a player's LP gain will be for a win/ what the penalty will be for a loss, because I am sincerely curious why Losses are penalizing me ~50% more than wins are rewarding me.

Thanks for your answers.