Trying to run "Grid Index Features" in ArcGIS Desktop and the "Page Name" field doesn't get populated properly.

[RoyceSimpson]

I'm trying to run the "Grid Index Features" tool to create a polygon grid for a map book.  For some reason, the "page name" field is being populated to start at B1 for page number 1... Shouldn't that start at A1?  I've run this thing 10 different ways and every time page number 1 has the page name of B1.  What am I missing on this?

[DanPatterson_Retired]

can you modify it using.... http://desktop.arcgis.com/en/arcmap/latest/map/page-layouts/modifying-the-grid-index-features-layer....