Using my Android phone, I applied the 6.0.38 upgrade to drone, Beacon and controller on April 2. This was the 911MB (large) one. Today April 13 I applied the 6.0.40 upgrade, again to drone, Beacon and controller. This was 239MB. I would guess that if you had skipped 6.0.38 and went directly to 6.0.40 it would show as being 911MB - as the attached screenshot from an above post shows.
I wish they would say exactly what changed rather than just "bug fixes under the hood and flying improvements". It's confusing when they don't consistently announce or not announce updates.