TWRP blowing away OS - user error?

For some TWRP is wiping my OS each time I install. Fortunately I can install the factory image, but sure what I'm doing wrong.
When I enter TWRP and try to install any files the Internal Storage is 0 MB
thanks in advance

Heres the Log
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Z:\NewNexus7Root\platform-tools>adb reboot bootloader

Z:\NewNexus7Root\platform-tools>fastboot flash recovery twrp-2.8.7.0-flo.img
sending 'recovery' (8956 KB)...
OKAY [ 0.291s]
writing 'recovery'...
OKAY [ 0.271s]
finished. total time: 0.564s

Z:\NewNexus7Root\platform-tools>adb reboot recovery
error: device not found
error: device not found