There are 2 tabs with fields that can be entered, which are also available in the main “ShareThis” settings (located under “System & Settings” – “Basics” – “ShareThis”). These tabs are “Button Size” and “User Names”. You can decide to not enter anything in these tabs at all. If you decide to do so, the block will always take the main settings. This is useful if you want to maintain all of your sharing settings on 1 single page. In case one of your social accounts change, your block instances will change along. If you have multiple accounts and some blocks need a different account attached, specify them in the block to override the main setting.
Tip: only fill in values under “Button Size” and “User Names” within a block if you need values that are different from your main settings (so you must have multiple accounts or want a different appearance/button size). If you want all instances to remain the same, use the main settings.