+x+xYour materials have their fibre orientation just as you have shown. Not always the longest side but usually lengthwise along the roll would be considered 0 deg.
But then you also have the orientation of your part or piece which is probably the more important thing when setting up/layup your fibres/layers/plys etc. For me then 0 degrees would be the lengthwise or longer direction of your piece or mould. For a tube 0 is lengthwise, etc.
The layup calls for +/-45 strips which i considered to be cut at +/-45 from my presumed 0 direction. the other guy was following the fiber direction as his 45, so cutting it parallel to the edge of the roll.
Often biaxial tapes are used as joins since all the fibres will pass across your join making it stronger. If this were the case then the tapes are cut across/90deg the roll or lengthwise/0 deg. The tape is the same either way. Tapes like this are also more flexible and easier for laying in complicated shapes.
I often cut regular 0-90 carbon cloths at 45deg across the roll just to create these more flexible DB tapes.