How long is a tick?

The manual says 1/3840th of a note

Yes, that is correct. 1/3840th of a whole note, or 1/960th of a quarter note, which is the usual measurement. (960ppqn or 960 Pulses Per Quarter Note)

also remember ticks are tempo based...meaning the slower the tempo, the larger the actual size of a tick.

ej

The format of the position info in the Event List is this

Bars beats divisions ticks
(unless you are in SMPTE view)
Which, if you have the division set to 1/16ths and the time signature set to 4/4 translates as :
1 bar (measure)= 4 beats (1/4 notes)
1 beat = 4 divisions (1/16th notes)
1 division (1/16th)=240 ticks