The number prior to the 1 (which is 1 second) are fractions and mean 1/ the number. The numbers after, with the ", denote actual time (secs). Hence on your scale:
1/4 = 0.25 seconds
1/1.3 = 0.77 seconds
1.3" = 1.3 seconds
Hope that is what you are asking :)
Matt
EDIT: Just noticed this is...