This is a common complaint from users, unfortunately it can be difficult explaining that memory is handled quite differently.. rest assured that if you have memory detected by OpenBSD, it won't be wasted.
Multiple "lists" exist in the kernel that track memory usage (..both physical and virtual), one of these is a list of "free" pages.. a page being 4096 bytes memory on most architectures.. memory that is immediately available to processes (..243 megabytes worth on your system).
As previously said, there are multiple lists.. it's more complicated then just "used memory" and "free memory", but the kernel is constantly updating all of these lists while using sophisticated heuristics to make sure the wheels keep turning.
The
vmstat(1)/
top(1) commands are useful at monitoring system resources, and the man pages do show you how to interpret the results.