If I remember correctly this token has a rebasing feature, I hope you understand this. I think the Meter Bridge doesn't want to take risks from AMPL's built-in features,
You should at least look for information whether Meter Bridge applies special conditions in exchanging these tokens, for example they set the rebase target price higher than the official one.
Rebased only happened once a day if I remember correctly and swap happened instantly in 1:1 basis. I believe the problem is on the meter bridge rate because they might using an outdated rate.
The AMPL price is at a stable price above 1 dollar which means rebase will give additional token to peg the price to 1 USD which in this case the OP should receive more. Nevertheless, swap should be 1:1 rate since it's instant while the rebase is once a day which will not affect the rate frequency unless the OP swap his token near the rebase period.