The Ps_Chalky has bigger dimensions than the other bmp files in the elemap folder in the brush settings post. It wouldn't work properly until I resized it to 63x63. I thought you should know.
Thank you for letting me know! Tumblr must have resized it or something, because I have it as 63×63 as well. I’ll add it to the description, but sadly it’s kind of out of my hands now.
Sorry for the trouble!