what is difference between na-nimittaggāhī and animitta?

Indriyasaṁvara is part of [sīlakkhandha](https://suttacentral.net/define/s%C4%ABlakkhandha) . there you see this > Idha, bhikkhave, bhikkhu cakkhunā rūpaṃ disvā **na-nimittaggāhī** hoti > nānubyañjanaggāhī. whereas **animitta cetosamādhi** is part of highest samadhi. Thats why it is after th 8th Jhana. > sabbanimittānañca amanasikāro, animittāya ca dhātuyā manasikāro. so with this background, and for the sake of proper practice, Can someone help in knowing what is the difference between **not grasping** nimitta (na nimittaggāhī) and **signless**(animitaa) ?