Format of a Directory Record in ISO9660

In ISO9660, there is are 7 bytes for recording date and time in driectory record. The last byte of these 7 bytes is as following:

Offset from Greenwich Mean Time in number of 15 min intervals from -48(west) to +52(east) recorded…

What does that mean?..
My guess is that for example, CET(Central European Standard Time) is 1 hr ahead of GMT (GMT+1), then I should set this byte to 0x04…(60/15*1)

Am I right?..

Thanks for reply.