Hi newbuild100
Been riding and organising proper (timecard) enduros for over 40 years so may be able to help.
Treat each part of the course between checks as completely separate timed sections. So if you arrive X minutes late at a check then you MUST add that X minutes to the times you are to arrive at every subsequent check, even if you are allowed to arrive a minute late at the checks without penalty, leave that for the organisers to sort out. If you arrive early at a check simply wait BEFORE the yellow flag for your correct time, as soon as you pass the yellow flag you are deemed to be at the check. It is normally worse to go into a check early rather that than late as you don't get a minutes allowance for being early. The ONLY time it is worth going into a check early is if you are close to going over the maximum allowed lateness (normally 60 minutes) then just go straight into any check as early as you can, anything to avoid going over the maximum lateness.
Start 09.10
Allowance 23min
Check 1 09.33 you ride the check in 20 minutes and arrive early so you wait until 09.33
Allowance 29min
Check 2 10.02 you ride the check in 30 minutes and therefore "lose" 1 minute (you are 1 minute late) so check in at 10.03 (10,03 + 1 = 10.03)
Allowance 11min
Check 3 10.13 you ride the check in 10 minutes but your correct time has now changed to 10.14 (still 1 minute later than the original) so you wait for you new correct time
Allowance 9min
Check 4 10.22 you ride the check in 9 minutes and your correct time is still 1 minute later than the original so you check in on time at 10.23 (10.22 + 1 = 10.23)
Allowance 18min
Check 5 10.40 you ride the check in 21 minutes so "lose" another 3 minutes so your new correct time is 10.44 (10.40 + 1 + 3 = 10.44)
Allowance 23min
Check 6 11.03 you ride the check in 24 minutes so "lose" another 1 minute so your new correct time is 11.08 (11.03 + 1 + 3 + 1 = 11.08)
Allowance 29min
Check 7 11.32 you ride the check in 25 minutes, 4 minutes early, but you must still add your 5 minutes lateness to your original time and check in at 11.37
Allowance 10min
Check 8 11.42 you ride the check in 13 minutes so "lose" another 3 minutes so your new correct time is 11.50 (11.42 + 1 + 3 + 1 + 3 = 11.50)
Allowance 8min
Check 9 11.50 you ride the check in 8 minutes so your correct time is still 8 minutes later than the original so you check in on time at 11.58 (11.50 + 1 + 3 + 1 + 3 = 11.58)
Allowance 15min
Finish 12.00 you ride the final check in 10 minutes but at the finish you can enter the check early without penalty so ride straight in whether your late or early.
Hope this helps, it seems a lot more complicated than it really is when I write it down, if I can ride and work it out then anyone can
If in any doubt just ask the guys riding with you or the guys at the check they'll always try and help.
What event are you riding?
The club I'm involved in, the Welsh Trail Riders Association (WTRA), are based in Llandovery, South/Mid Wales and "we" "invented" forestry timecard enduros, Hare & Hounds, short course enduros, and trail bike rallies.