Antisplog Out of memory (allocated 27000832) (tried to allocate 197540 bytes) in /home/.../public_ht

Hi, I'm setting some blog as spam... when i try to delete all them in mass i get this:

Fatal error: Out of memory (allocated 27000832) (tried to allocate 197540 bytes) in /home/.../public_html/wp-includes/functions.php on line 251

Just some blogs are deleted, the others are not, and i've to do it again, and again, and again... it's kinda stressfull

I've set the max memory in the php.ini and the wp-settings.php to 1512MB... i don't think it's because it's too low... how much would require otherwise? 64GB?