I'm not sure, but something might be wrong here...
Looking at this 2 lines
glc_s = SDC_buffer[24] ' get the current lap count into tmp var ( Nmath wont allow indexed var)
@ MOVE?BP _glc_s,_Tmp32bit_1 ' copy lap value into tmp1
And you sad that you have array of bytes.
So glc_s is byte, and max time that can hold is 255 sec.
And then I lost it...
Why you bother with N bit math if your max result is only byte wide? There is more than 255sec in day, so day will be 0 always, even hour...
You are doing something fundamentally wrong here.