Electron / photo - memory usage

I have firmware that can be run on both a Photon or an Electron - have to re-target the compile. The puzzle is when I look at the memory usage as displayed by the consoles:

51kB of 111kB RAM used

62kB of 81kB RAM used

I can understand the available RAM might be different but am confused as to while the usage is different by 11K. Both data samples were taken after the firmware is download and run for about 60 minutes to reach a steady state of usage and the usage number do not change over time. All String variable have the same reserved length.

What am I missing or are the usage number not measuring the same thing?

Thank you

While the system part and user part are separate flash sectors, the system and user part share a single heap for dynamic RAM allocation. The system does not run in a protected space.

Cellular devices (a socket interface over the u-blox cellular modem with an AT command interface) vs. Wi-Fi (Cypress WICED API running LwIP on the STM32) just have different RAM requirements, leading to a different amount of base usage.