Imagine HWH-MAS Coromandel Express has a single Tatkal Quota from HWH to VSKP and HWH-MAS (Both sharing quota) and another Tatkal Quota from VSKP-MAS
Now imagine the same train having single quota from HWH to MAS (Meaning any Tatkal booking for any two given stations [provided it is allowed and does not come under distance restriction] will be allotted berth out of this single quota.
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All...
more... the above shows that Tatkal booking happens strictly out of the quota provided against the desired journey leg and no sharing/overlapping happens like General Quota booking. This is point to point quota.