Chain BreakingForum-Index → Help → Chain Breaking
Important: Only eggs that are obtained from the Lab, the Daycare, the Gem Collector, the Safari, the Ancient Cave*, the Event Shop or found in the Tall Grass count for your chain.
*Excluding Harvest Sprites
Which means those kind of eggs will only break your chain if it's a different Pokémon than the one in your current chain (i.e. NOT eevee, etc.) is..
So, if it's an Eevee (like on your chain, etc.) egg from the Tall Grass.. it will just count for your (i.e. Eevee, etc.) chain instead.