In your particular example Total memory usage is sum of all caches allocated memory in Android HWUI library
Caches:
Current memory usage / total memory usage (bytes):
TextureCache 74625498 / 75497472
LayerCache 3538944 / 50331648 (numLayers = 3)
Layer size 1440x810; isTextureLayer()=1; texid=24 fbo=0; refs=1
Layer size 1440x810; isTextureLayer()=1; texid=42 fbo=0; refs=1
Layer size 1440x810; isTextureLayer()=1; texid=48 fbo=0; refs=1
Layer size 1344x192; isTextureLayer()=0; texid=40 fbo=0; refs=1
Layer size 1472x192; isTextureLayer()=0; texid=41 fbo=0; refs=1
Layer size 1344x256; isTextureLayer()=0; texid=23 fbo=0; refs=1
Layers total 17535744 (numLayers = 6)
RenderBufferCache 0 / 8388608
GradientCache 32768 / 1048576
PathCache 1260 / 33554432
TessellationCache 0 / 1048576
TextDropShadowCache 0 / 6291456
PatchCache 128 / 131072
FontRenderer 0 A8 1048576 / 1048576
FontRenderer 0 RGBA 0 / 0
FontRenderer 0 total 1048576 / 1048576
Other:
FboCache 0 / 0
Total memory usage:
93243974 bytes, 88.92 MB
The total memory 88.92 MB is the sum of allocated memory for TextureCache + Layers total + ... + FboCache
This output goes from the Android HWUI library - which is implementation of Android UI drawing based on OpenGL HW accelerated library
More details could be read in the sources, for example here