Based on the link Jealoushe posted you only need two qualifying Pre-Training scores if you are a junior, to move up to Training.
Am I reading that right?
Training (Senior Competitors) - Open to all competitors and horses (not necessarily
as a combination) until they have completed 3 events
at the Preliminary level or above during the previous
2 calendar years
The footnote at the bottom reads:
For the purposes of Junior Competitors wishing to upgrade to training – Competitors must have
completed a minimum of two events at the Pre-Training level. One event must have 0 jumping penalties in
the Cross Country phase, and one event may have no more that 20 jumping penalties in the Cross Country
phase. All other qualifications shown above must also be met.