diff --git a/DataGuide_AAPF_HSI.md b/DataGuide_AAPF_HSI.md
index e75f479..21be4b0 100644
--- a/DataGuide_AAPF_HSI.md
+++ b/DataGuide_AAPF_HSI.md
@@ -76,6 +76,39 @@ This document details the file system organization and navigation procedures for
 
 ### How to Read Information in Spreadsheet file (.xlsx, masterfile)
 
+The spreadsheets contains various phenotypic measurements derived from the HSI data and auxiliary measurement info. Here's a breakdown of the column headers:
+
+- `Filename-VNIR-SIDE`
+    - Filename of input VNIR-SIDE data
+- `Filename-VNIR-TOP`
+    - Filename of input VNIR-TOP data
+- `Filename-SWIR-SIDE`
+    - Filename of input SWIR-SIDE data
+- `Filename-SWIR-TOP`
+    - Filename of input SWIR-TOP data
+- `EXP ID`
+    - Internal experiment number assigned in PPEW
+- `POT_BARCODE`
+    - Unique number assigned to plant
+- `VARIETY`
+    - Variety assigned in PPEW
+- `TREATMENT`
+    - Treatment applied to plant
+- `SCAN_TIME`
+    - Scan start time
+- `SCAN_DATE`
+    - Scan start date
+- `DFP`
+    - Age of plant in days from planting at time of imaging
+- `{vegetation index}_{statistic}`
+    - Statistics of vegetation indices over vegetation mask area. See below for more detail.
+- `Wavelength in nm`
+    - Average reflectance over vegetation mask area (ratio of reflected energy to incident energy)
+
+
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+