Testosterone levels vary in a 24hr cycle. For consistency, always have it measured as a fasting blood test first thing in the morning. I've no idea how much you might expect it to vary during the day when on ADT, so I don't know if that explains the difference.
It may vary during the injection cycle (particularly at the end), if the injection dose is marginal for you, or if it wasn't injected correctly causing it to run out faster than it should. We did have a member here who had to have the injections more often to keep his Testosterone low, although that's the only time I've heard of that being done.
There is no universally accepted castrate level, but 1.2 is sometimes held to be the castrate level, and is the level below which the hormone injections should be able to maintain Testosterone level. However, they often achieve better than this, 0.7 or lower being common. Sometimes one of the drugs doesn't work so well in someone, and changing to another works better. When you're on life-long ADT, getting the Testosterone level as low as possible may be more important than for those on time-limited ADT.
When ADT fails and you become castrate resistant, this isn't due to increasing Testosterone levels, it's due to the cancer growing in spite of low Testosterone levels. So what you're seeing isn't that. It may be that keeping Testosterone levels as low as possible helps make the time before you become castrate resistant as long as possible, so I think it is worth seeing if you can get Testosterone lower.