Reinstated means the judge put you back on probation instead of permanently revoking your probation and sending you to prison.
The time on your probation was tolled between the revocations and reinstatements, which means the clock stopped running. Your five years of probation will be extended by the amount of time it was in revoked status.
The clock stops when the judge revokes your probation. Once reinstated, you're put back on probation and the clock starts again. Your original date when probation was set to expire likely got extended for the same amount of time your probation was revoked.
For example, if your probation started in 2007 and was for 5 years, it normally would have expired in 2012, five years from the date of your sentencing. If your probation was revoked in 2009 and it was revoked for 6 months, once you were reinstated, probation would have started again from the reinstatement date, but you would not get credit for that six months you were revoked. Your probation would now expire 6 months later than it was originally set to expire.