Testing and experimenting with YT playing in Brave browser as of 2025-01-09 (YYYY-MM-DD)...

• The % was vital (whereas in an article I initially read, this character was omitted)
• line 0% worked as expected - putting the text at the top
• line 1% did exactly the same; likewise for line 2
• line 3 up to line 100% instead put the text at the bottom (YT's default position). Implying no ability (through this method at least) to obtain arbitrary vertical alignments.
• align:left position:0% size:50% worked as expected
• Regarding the position value in the latter: 0%, 2%, 5%, 8% progressively rightwards-shifted the (left) anchor (alignment-point) of the text. However 1%, 4%, 10% gave no change from their respective predecessor-numbers.