Blast procs consist of two distinct status effect components – the normal stun on recovering victims which is displayed by the icon and the knockdown which isn't depicted – that can stack for additionally increased damage, up to 720.58x with the procs listed above.
The damage increase from the knockdown lingers briefly longer than the one of the depicted icon.
Note that conditions or abilities that prevent knockdowns (e.g. Bastille) will hinder the second component from increasing damage.
The bonus damage is not applied to a hit which inflicted a new status effect; that means if a melee strike inflicts the first status effect onto a target, then this strike's damage (including its status effect and every DoT tick until the duration ends) will not be amplified by 1.6x. Only subsequent strikes will be amplified. Therefore, if a target already dies from the first strike that inflicts a status effect then Condition Overload is not of any use; it only is if the target survives this first strike.
You cannot gain additional bonus damage by stacking multiple instances of the same status effect. For example, multiple instances of Slash or Toxin status effects.
To achieve a high amount of distinct status procs, it is advised to use melee weapons that feature high attack speed with high base status chance and IPS like the Lesion or Glaive Prime. To achieve a high amount of distinct status procs for ranged weapons, it is advised to use weapons that feature high fire rate or AoE with innate elemental status, such as Staticor or Pox.
It's also a good idea to use it when running any Warframe that can also inflict status, such as Saryn, Ember, Volt, or Equinox.
Sentinels and their weapons are additional, viable sources for status effects: