have a fix on (something)

To have a firm, clear understanding or determination of something. I hope everyone has a fix on the material, as you'll be tested on it next week. I thought I had a pretty good fix on English idioms, but I don't understand this one at all!

Common Names:

Name	Pronounced	Usage
ŠPela	-	Slovene
Wulfno&Eth;	-	Anglo-Saxon
Patricia	pə-TRISH-ə (English), pah-TREE-thyah (Spanish), pah-TREE-syah (Latin American Spanish), pah-TREE-tsee-ah (German)	English, Spanish, German, Late Roman
Jun-Ho	joon-ho	Korean
Tyra	-	Swedish, Norwegian, Danish
Varinius	-	Ancient Roman