php memory limit discrepancy between virtualmin>services>php configuration and Wordpress>revolution slider

I have a strange thing going on with memory limits…

According to Virtualmin>services>php 7.2 Configuration>resource Limits

Memory and transfer limit options
Maximum memory allocation Default
128M
Maximum HTTP POST size Default
32M
Maximum file upload size Default
32M
Maximum execution time Default
180
seconds
Maximum input parsing time Default
180
seconds

but revolution slider in Wordpress says the following…

System Requirements

uploads folder writable = yes
memory limit = 256MB
Upload max filezie=32MB
Max.Post size = 32MB




so how does one explain the discrepancy on memory limits? (Virtualmin says 128MB and wordpress is reporting 256MB)