The Current Frame as Drawing Name option can be enabled in the Preferences panel, under the Exposure Sheet tab. Use this preference to automatically name the drawing corresponding to the frame position, this avoids numbering conflicts while animating.
For example, using the default preferences, you start with the first drawing on frame 1, this drawing is called 1. You then draw the extreme position drawing on frame 10, this drawing is called 2. Next, the in-between pose is drawn on frame 5, this drawing is called 3 and so on.
At the end, you have a sequence like this: 1-9-4-6-3-8-5-7-10-2.
Instead, using the Use Current Frame as Drawing Name preference, each drawing is automatically named by its frame number and the sequence looks like: 1-2-3-4-5-6-7-8-9-10.
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