Primepulse is an initial injection event of the configured pusle width (in your case it was 8ms) on power up prior to any cranking activity. It is scaled down as the engine warms up, to the % configured
Cranking threshold is the RPM value that determines whether the engine is in a cranking phase or a running phase. Below this threshold, a fixed VE and ignition value as configured, are used. above this threshold the VE table and spark table are used.
There are explanations of all these settings in Vemstune if you press the F1 key when you have the configuration table open.