The “virtual memory size” (VSZ) listed in ps isn’t what you think it is. That is the total size of the address space assigned to the executable, which includes code, data, memory-mapped files, shared libraries, swap usage, and pages that have been allocated but not actually used yet. It’s not uncommon for that to be very large; I’ve got a virtual machine running right now whose VSZ is about 46 GB…
You should actually pay attention to the resident set size (RSS), which is how much physical memory the task is actually using. In your case, 10,320 kB seems more reasonable.