Tentative
Temporary
noun, prefix, の adjective
Temporarily determine something. That makes it tentative and temporary.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
こちらの料金設定は暫定的ですのでご留意下さいませ。
Please bear in mind that these prices are temporary.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.