Question about Red Sign Soapstone

I need to know what exactly the level requisites (if there are any) are for it, the wiki says, "there is no upper limit on who can summon you, but with the soapstone a
player on your level range can summon you. Even being lower level. Meaning That a level 150 can summon a level 120, but a level 120 could NOT summon a level 150."

So that means lower level players can't summon higher levels, but higher levels can summon lower levels? If that's true then is there a limit on the difference in level (example: sl700 summoning a sl1)?

There is no upper limit. Maening a 700 could summon a 150. That's what makes it good for trade. Only lower leveled players you are in the level range of can see the sign.

https://soulswiki.forumotion.com/t14670-all-of-the-exact-level-ranges-matchmaking-formulas-for-the-multiplayer-items
Here you go.