据Cambridge Dictionary解释，equivalent作名词时表示“something that has the same amount, value, purpose, qualities, etc. as something else”。从上述解释可以看出，equivalent表示“等同”(same)，通过以下例句方便理解：

The SAR government announced it issued US dollar and euro-denominated green bonds equivalent to $3 billion in total.

香港特区政府宣布成功发售新一批绿色债券，总值30亿美元，包括美元债和欧元债。

Our basic estimate at the moment is that the operating cost here for this aircraft will be the equivalent of $1 per passenger over a 25-mile trip.

据我们目前粗略估算，这款飞机在圣保罗的运营成本相当于25英里范围内每名乘客1美元(约合人民币6元)。

Deep Dive Dubai is filled with 14 million liters of water - an amount equivalent to nearly six Olympic-sized swimming pools.

“深潜迪拜”水量达1400万升，相当于6个奥运会泳池的注水量。

The board of governors of the International Monetary Fund has approved a new general allocation of Special Drawing Rights equivalent to 650 billion US dollars, in an effort to boost global liquidity amid the COVID-19 pandemic.

IMF理事会批准了规模为6500亿美元的新一轮特别提款权(SDR)普遍分配，以在新冠疫情期间增加全球流动性。

因此，Equivalent of后加金额应译为“相当于”。至于“约合”，其意思为“大约折合”，主要用于换算，并非完全相等。

参考：

中国日报网