Hi,
the macro command /wait currently accepts only 'whole number' digits between 0 and 60 as parameter.
GUI interface (ie hotbars) displays ability and spell cast/recast times to two decimal places (ie, my "Summon" spell cast time is 5.91 seconds).
If you use one or two decimal places in your /wait macro, the number will be rounded to zero decimal places by the game interface.
Queuing of abilities allows you to use ability 0.5s before global cooldown is ready, which means, if I was using "Summon" as part of my macro, I could execute next ability after 5.41 seconds.
But because the macro GUI uses only whole numbers, I need to /wait 6
I was just robbed of 0.59s of my life (or 9.83% of it, in the long term).
If I was doing Titan (Hard) and spamming "Summon" was the difference between win and lose:

I could cast the spell manually approximately 227 times.
Using the in-game macro system, I could cast the same spell only approximately 211 times. (1800 seconds divided by spell cast time and 2.5s global cooldown).
'Whole number' macro is a relic from FFXI and the world has sped up since 11 years ago.

The conclusion:
Please allow us to use /wait xx.xx in macros instead of /wait xx