Gallery Widgets: Inline Styles Do Not Adhere to $Content_Width

JetPack Gallery Widgets do NOT appear to inherit $content_width from functions.php (specifically in a sidebar)… These Widgets add inline widths narrower than BOTH their container AND $content_width – while standard Text Widgets display at correct/wider width… (Underscores Theme is under development so should not be theme-related). Please advise…