The common practice is not to describe page layout in a comic script – that's typically the domain of the penciller.

If you want to suggest or prescribe a layout to the artist, you can insert a thumbnail in your script. The comic script format itself does not have a convention for describing or including layout – you'll have to insert an image.

Here is an example of a page from Archie Goodwin’s script for Batman: Night Cries, including a suggested layout, as it was reprinted in The DC Comics Guide to Writing Comics by Dennis O'Neill:

I think an image is easier to understand than your percentages.

The common practice is not to describe page layout in a comic script at all – that's typically the domain of the penciller.

If you want to suggest or prescribe a layout to the artist, you can insert a thumbnail in your script. The comic script format itself does not have a convention for describing or including layout – you'll have to insert an image.

Here is an example of a page from Archie Goodwin’s script for Batman: Night Cries, including a suggested layout, as it was reprinted in The DC Comics Guide to Writing Comics by Dennis O'Neill:

I think an image is easier to understand than your percentages.