Can't diminution or boost ability value of -webkit-transform

Given this code:$('#slider').css('-webkit-transform',
'translate(-=950px)');It won't do anything. If we manually set a value of
interpret to for instance -1000px, executing a above formula only removes
a ability completely, as if there was an blunder parsing it.Is
incrementing or decrementing ability value indeed illusory with CSS
transforms?