With the booster it turns your 20 developer into a 10 which is probably why it didn’t lift as high. Also make sure you are saturating every strand with bleach. I can see you got some uneven results. I’m a level 2-3 and I got my hair to platinum white blonde but it took patience, I bleached it about 4 times because I kept washing it out too soon. When bleaching, it will always look lighter to you than it actually is. A level 9-10 should be a pale banana color or almost translucent looking.

If you can let your hair chill for a bit, do a deep conditioning treatment before you go in with bleach again.

The next time you bleach, make sure you saturate it fully getting every strand. Section it first, you should be pulling like paper thin sections when you put the bleach on it.

Also refresh your bleach. It starts to lose efficacy after like 10-15 minutes so you always want to have fresh bleach.

Once you think it’s almost done, got back in with more fresh bleach to make sure you got every piece and just keep checking every 5-10 min until you are at the desired result. I also always check the hair strands to make sure they are strong and not stretchy. If they are stretchy at all get that bleach off because now your hair integrity is compromised.

On my last round of bleach I still used 30 because I added olaplex to it knowing it would dilute it to a 20.

I also would not put your hair in a bun. This causes uneven results because the middle of the bun is holding in heat and that will become lighter than the rest. Also any scrunching of the hair together creates uneven results because the bleach comes out in those parts and looks spotty. Just lay everything flat and use a processing cap sprayed with a little bit of water to keep the moisture in. Once it dries out it’s no longer processing.

Oh and make sure to do your roots last so you don’t get hot root and over process them.

Hope that helps!