What does it mean?

I feel like I'm getting the wrong impression, I've not been much of a breeder or shower with my horses since I've joined, I'm mainly here for the art but I've recently had time to start my own lines of horses and have noticed that all my horses have base stats, current stats and then a +33 or whatever number it is.

So one of my stallions has this:
STR: 25 +10
SPD: 21 +10
AGI: 37 +35
INT: 44 +35
END: 22 +10
ALL: 149
Does this mean he has 31 in Speed? Or 32 in Endurance? Rather than the 21 or the 22? Because I don't understand the plus sign? When do their stats get updated if they are added stats? I'm so confused. xD

The first numbers are his stats, the +10 etc are the stats given to him by the tack he's wearing. When competing in shows it will consider the sum of these, i.e. he effectively has 31 in speed, etc. But when breeding tack will not be a factor, so the foal's stats will depend only on the first number.

the pluses (which will be in green text) are the bonus stats added by the tack that the horse is wearing. they're not actually stats that your horse has (since they'll disappear if you untack them), but they ARE counted in the stats of the horse when they are competing in shows. Higher grade tack will give higher bonuses, which will make the horse more competitive in shows (assuming they are wearing the tack for their discipline)

does that help?
:)

Yes! Thank you guys. Also what are the best ways to raise stats? I feel its taking me ages to get my foundies to 200 stats. I'm treating peppermints, training in arenas and doing 10 hours of schooling a day for each one. Is that a good way to raise stats?

Show winnings can give stats as well, I find that mine go up pretty quickly this way.

Showing horses typically gives much more stats than schooling, so try that.

like Cheshire Kitty and Ulysses Blue said, showing is a better way to gain stats. However, since you've been treating with Peppermints, it's likely that your horses will have high non-specialty stats, which can negatively affect their ability to do well in showing.

I'd suggest either continuing as you are, or converting their discipline (assuming they are foundations, otherwise you'll have to pay the 10k to convert and then the 2 credits to convert back, which is pretty expensive).