Hello,
This warning message indicates that Easy::Apache is only able to verify 259 Megabytes of memory is currently available for use. Other processes/daemons running in your
VPS are using enough memory to trigger this warning.
Upgrading to a higher-memory plan (something that includes 253 more Megabytes of memory,
512 - 259 = 253) would eliminate this warning message
(assuming your memory usage is constant), as would shutting down other services/daemons (even temporarily, like for the duration of the Apache Upgrade process) to free up 253MB of memory.